"For surely our whole life is involved in a constant battle in which our salvation itself is at stake; nothing is more disgraceful for a Christian than cowardice."

Pope Leo XIII, Inimica Vis (7)

"For heresies, and certain tenets of perversity, ensnaring souls and hurling them into the deep, have not sprung up except when good Scriptures are not rightly understood, and when that in them which is not rightly understood is rashly and boldly asserted."

St. Augustine, Treatise 18 on John 5

"The devil also speaks about Scripture, and all the heresies, according to Ezekiel [13:18], take material from it and sew together pillows which they place under the elbow of every age. As for me, when I have Christ in me as I speak, I do not have the gospel of man. [...] Great harm is done to the Church when by means of some perverse interpretation the Gospel of Christ turns into the gospel of man—or, what is worse, the gospel of the devil."

St. Jerome, Commentary on Galatians 1:11-12

"In truth, sudden uprisings and the boldest rebellions immediately followed in Germany the so-called Reformation,[referring to the German Peasants' Revolt] the authors and leaders of which, by their new doctrines, attacked at the very foundation religious and civil authority; and this with so fearful an outburst of civil war and with such slaughter that there was scarcely any place free from tumult and bloodshed. From this heresy there arose in the last century a false philosophy — a new right as it is called, and a popular authority, together with an unbridled license which many regard as the only true liberty. Hence we have reached the limit of horrors, to wit, communism, socialism, nihilism, hideous deformities of the civil society of men and almost its ruin."

Pope Leo XIII, Diuturnum (23)

“Read assiduously and learn as much as you can. Let sleep find you holding your Bible, and when your head nods let it be resting on the sacred page.”

St. Jerome, Letter 22 To Eustochium (17)

Q: Who, besides apostates and heretics, sin against the Faith?

A: Besides apostates and heretics, the following sin against the Faith:
i. unbaptized people who repudiate the faith after it has been sufficiently clearly put before them—this is “positive infidelity” ;
ii. people who neglect to secure sufficient religious instruction such as suits their age and condition in life ;
iii. people who embrace errors condemned by the Church and which approximate more or less to heresy ;
iv. people who deliberately expose themselves to the danger of losing their faith—those, for example, who without leave and due precautions read books prohibited by the Church, especially books written by apostates, heretics or schismatics in defense of their apostasy, heresy or schism.

The 1932 Catholic Catechism, 523

November 27, 1095

"Oh, race of Franks, race from across the mountains, race chosen and beloved by God, as shines forth in very many of your works set apart from all nations by the situation of your country, as well as by your Catholic Faith and the honor of the Holy Church!
From the confines of Jerusalem and the city of Constantinople a horrible tale has gone forth... that a race from the kingdom of the Persians, an accursed race... has invaded the lands of those Christians and has depopulated them by the sword, pillage and fire...
Let the deeds of your ancestors move you and incite your minds to manly achievements; the glory and greatness of King Charles the Great and of your other kings... Oh, most valiant soldiers and descendants of invincible ancestors, be not degenerate, but recall the valor of your progenitors...
Accordingly undertake this journey for the remission of your sins, with the assurance of the imperishable glory of the Kingdom of Heaven."

Bl. Urban II's Speech at Clermont

Sorry this is so spliced, the character limit's 1024 with media. The entire speech is worth reading, would highly recommend!

"So vast is the number of heretics and so great their diversity in dogma, that, though among themselves they differ greatly in opinions and doctrines, in their hatred of us, they are of one accord. Just as Herod and Pilate, for example, who were enemies, made their peace in persecuting Christ, and were more formidable in their amity than their enmity, so the heretics, impiously at variance, league together for still greater impiety."

St. Jerome, Homilies on the Psalms: Homily 62, Psalm 82

"It is the hope and prayer of all of us who profess the Catholic Faith that heresy be refuted and individuals be converted. Or, if they choose to persist in error, the blame is certainly not to be placed on us…, but rather on those who have preferred falsehood to truth."

St. Jerome, The Dialogue Against the Pelagians, Book I, Preface, paragraph 2

"Heretics are never constant in their convictions, but are forever changing their opinions, shifting back and forth."

St. Jerome, Homilies on the Psalms: Homily 68, Psalm 90

Do not be dismayed by this disaster. God chastises every son whom he accepts, so perhaps he has chastised you more because he loves you more. Jerusalem, a city loved by God was destroyed, with the Temple of God, in Babylonian flames. Rome, surrounded by its company of holy apostles and countless martyrs, was devastated by the heathen, but quickly recovered through the goodness of God. Almost the whole of Europe has been denuded with fire and sword by Goths and Huns, but now by God's mercy is as bright with churches as the sky with stars and in them the offices of the Christian religion grow and flourish. Encourage each other, saying, "Let us return to the Lord our God, for he is very forgiving and never deserts those who hope in him."

St. Alcuin of York, Letter to Bishop Higbald concerning the Viking raid on Lindisfarne in 793

'Let them fall by their own devices.' Excellently said, 'by their own devices,' for heretics change or alter their doctrine from day to day. In fact, if a theologian learned in the Scriptures contends with them, overwhelming them with proof from the Sacred Books, what do they do but straightway look around in search of a new doctrine. They do not seek knowledge for the sake of salvation, but look around for new doctrine to vanquish the opponent; hence, the psalmist said: 'Let them fall by their own devices. Let them fall by their own countless contrivances and let them have but one recourse, You, my God.

St. Jerome, Homilies on the Psalms, Homily 2: Psalm 5

"For beauty of face, elegance of movement, an affected gait and lisping voice, penciled eyebrows and enamelled cheeks, elaborate braiding and dyeing of hair, costliness of dress, variety of golden ornaments, and the glory of precious stones, the scent of perfumes, and all those other matters to which womankind devote themselves, are enough to disorder the mind, unless it happen to be hardened against them, through much austerity of self restraint."

St. John Chrysostom, On the Priesthood, Book VI, 2

Those who have a difficulty in believing seek a reason in the fact that the Jews do not believe. "Were this so clear," say they, "why did the Jews not believe?" And they almost wish that they had believed, so as not to be kept back by the example of their refusal. But it is their very refusal that is the foundation of our faith. We should be much less disposed to the faith, if they were on our side. We should then have a more ample pretext. The wonderful thing is to have made the Jews great lovers of the things foretold, and great enemies of their fulfilment.

If the Jews had all been converted by Jesus Christ, we should have none but questionable witnesses. And if they had been entirely destroyed, we should have no witnesses at all.

Blaise Pascal, Pensées, Section XII, 745 & 750

We are told in Holy Scripture to be careful of time, which is the most precious thing and the greatest gift that God bestows upon living man. The Pagans even understood the value of time. Seneca observed that “the value of time is priceless.” . . . Time is a treasure which can be found in this life alone; it is to be found neither in Heaven nor in Hell. This is the lamentation of the lost in hell, “Oh, that an hour were given.” They would give anything for one hour in which they might be able to remedy their ruin, but this hour they will never have. In heaven there are no tears; but if the blessed could weep, this would be a cause for lamentation, that they had lost any time during this life in which they might have acquired greater glory – for such time they now can never have.

St. Alphonsus Liguori, Preparation for Death

But, as no society can hold together unless some one be over all, directing all to strive earnestly for the common good, every body politic must have a ruling authority, and this authority, no less than society itself, has its source in nature, and has, consequently, God for its Author. Hence, it follows that all public power must proceed from God. For God alone is the true and supreme Lord of the world. Everything, without exception, must be subject to Him, and must serve him, so that whosoever holds the right to govern holds it from one sole and single source, namely, God, the sovereign Ruler of all. “There is no power but from God.” [Romans 13:1]

Pope Leo XIII, Immortale Dei (3)

"Yet again, the Jews who thus control international finance are at work in many other capacities. . . I may be told that to put an end to this state of affairs is impossible so long as parliamentary government, with its profound corruption, endures; that the only force capable of dealing with the plutocratic evil of alien monopoly upon this scale is a king; and that a king we have not, among modern nations. To which I answer that the parliamentary system will not last for ever. It is already in active dissolution among ourselves, and badly hit elsewhere. The king may not be so far off as people think him to be."

Hilaire Belloc, The Jews, Chapter 4, The General Causes of Friction, pg. 96

"But let not your fasts be with the hypocrites; (Matthew 6:16) for they fast on the second and fifth day of the week; but fast on the fourth day and the Preparation (Friday). Neither pray as the hypocrites; but as the Lord commanded in His Gospel, thus pray: Our Father who art in heaven, hallowed be Your name. Your kingdom come. Your will be done, as in heaven, so on earth. Give us today our daily (needful) bread, and forgive us our debt as we also forgive our debtors. And bring us not into temptation, but deliver us from the evil one (or, evil); for Yours is the power and the glory forever. Thrice in the day thus pray."

The Didache, Chapter 8. Concerning Fasting and Prayer (the Lord's Prayer) [circa 70 AD]

"Fasting is of great benefit to the Christian soul. It humbles the body and with the humiliation of the body, the soul, too, is humbled; but although the body has been reduced to submission, the soul nevertheless suffers its own passions. Now if to the flame of the soul is added the flame of the body, who is able to endure such twofold burning? Prayer frequently extinguishes the fire of the soul, and likewise does trust in the Lord."

St. Jerome, Homily on the Psalms: Homily 33 on Psalm 106

"For the saint, every day is the day of Christ’s Resurrection, and he always feeds on the Lord’s flesh. But days for fasting and gathering together for worship were instituted by prudent men for the sake of those who leave more time for the world than for God, and are unable, or rather unwilling, to congregate in church every moment of their lives, or to put the offering of the sacrifice of their prayers to God ahead of their human activities. For how few people are there who always observe at least these few regulations about the times of prayer or fasting? Thus, we are allowed to fast always, to pray always, and to celebrate unceasingly and joyfully in the Lord’s day by receiving his body."

St. Jerome, Commentary on Galatians 4:10-11: "You observe days, and months, and seasons, and years! I am afraid I have labored over you in vain."