Ibn al-Qayyim رحمه الله:

“There is a connection between the eyes and the heart — whatever one of them engages in, the other will engage in. When one is good, the other will be good; when one is corrupt, the other will be corrupt. If the heart is corrupt, the eyes will be corrupt, and if the eyes are corrupt, the heart will be corrupt. His heart becomes like a dunghill, which is the place of filth and impurities.

Consequently, his heart is not suitable to house knowledge of Allāh, love for Him, devotion towards Him, and happiness from nearness to Him. It is only suitable to house its opposite.”

[One Hundred Pieces of Advice | Pg. 31]

Sheikh Uthaymin (‏رحمه الله) mentioned the following:

[من طهر قلبه من المعاصي كان أفهم للقرآن ومن تنجس قلبه بالمعاصي كان أبعد فهما عن القرآن.]

"Whoever purifies his heart from sins will have more understanding of the Quran, but whoever sullies his heart with sins will be further from understanding the Quran."

[Al-Qawl al-Mufeed 'alā Kitab al-Tawheed 2/37]

Shaykh Saalih al Fawzan (حفظه الله) said:
“The speech of the scholars is not a proof. Proofs are verses from the Quran or Hadeeths of the Messenger (ﷺ). As for the speech of the scholars, then their speech explains and clarifies the verses from the Quran and the Hadeeths of the messenger, and it is not that their speech is a proof in itself.”
[Shaykh Saleh Al-Fawzaan, Expl. Al-Usool Al-Thalaatha, pg. 24]

Imām Maalik (رحمة الله) said:
“Every statement will either be accepted (when it is in agreement with the Quran and Sunnah on the understanding of the Salaf) or rejected (when it opposes that) except for the speech of the inhabitant of this grave (of the Prophet Muhammad (ﷺ) since he was protected by Allah from making mistakes in the religion, his speech is never rejected)”
[Siyaar ‘Alaam an-Nubalaa 8/93]

Shaykh Muhammad Ibn Saleh Al Uthaymeen (رحمة الله) said:
“A person who only sticks to one Imaam no matter what and ignores everything else has taken this Imaam as a Messenger.”
[Sharah Ul-Usool, Pg. 599]

Shaykh Muhammad Nasir ud Deen Al Albanee (رحمة الله) said:
“So aspire, O Muslim, to know your Islaam from your Lord’s Book and your Prophet’s (ﷺ) Sunnah. And don’t say, ‘So and so said.’ For verily, the Truth is not known by the men nay, know the Truth, you will recognize the men.”
[As-Saheehah, 5/350]

‘Umar ibn al-Khattab expressing his fear of being questioned by Allaah:

"I wish I was not created.
I wish my mother never delivered me.
I wish I was nothing.
I wish I was totally forgotten."

● {Az-Zuhd of Ibn al-Mubarak (235)}

"Do not ask children of Ādam of any need.

Ask the One whose doors are never closed.

Allāh gets angry if you abandon asking Him,

But the children of Ādam get angry when they are asked."

['al-Uzlah | p.67]

﴾فَبِأَىِّ ءَالاءِ رَبِّكُمَا تُكَذِّبَان﴿ِ

This says: Then which of the blessings of your Lord will you both deny?

This means: Favors that are obvious to you while you are surrounded by them, you cannot deny or reject them.

So we say, just as the believers among the Jinns said: “O Allaah! None of Your favors do we deny. All praise is due to you!”

● {تفسير ابن كثير ٥٥:١٣}

Ubaid Ibn 'Omair رحمه الله used to say if winter came:

"O people of the Qur'ān, the nights have lengthened for your prayers and the days have shortened for your fasting so take advantage."

● [المصنف لابن أبي شيبة ٩٨٣٦]

Ibn Al-Qayyim رحمه الله said:
"If one does not spend one's time for Allah's sake, then it is better to die."
[Ad-Da, p. 183]

Imaam Ibn Taymiyyah On Abandoning The Needs Of One's Wife.

قال شيخ الإسلام ابن تيمية رحمه الله : وحصول الضرر للزوجة بترك الوطء مقتض للفسخ بكل حال، سواء كان بقصد من الزوج أو بغير قصد، ولو مع قدرته وعجزه، كالنفقة وأولى..

Shaykh-ul-Islām Ibn Taymiyyah رحمه الله: “If for the wife there is harm due to abandonment/lack of sexual intercourse then it is an adequate cause for separation (between the husband and wife) in all cases whether the husband does that intentionally or unintentionally whether he is able or unable, it is like maintenance (food, clothes and shelter) and (probably) even more important.”

● [الفتاوى الكبرى ٥\٤٨١-٤٨٢]

Ibn Taymiyyah: “Regarding sexual intercourse, it’s obligatory (upon the husband) once every 4 months or according to her need and ability.”

● [مجموع الفتاوى ٣٢\٢٨١]

Īsā عليه السلام said: “Place your treasures in heaven, for a man’s heart is where his treasure is.”

‎● {كتاب الزهد الإمام أحمد بن حنبل ٣١٣}

Allāh said: "Do not think that I will not give you if you ask Me for great things, and do not feel too shy to ask Me for small things."

● {Fayd al-Qadeer (v. 4, p. 110)}

Ibn al-Qayyim رحمه الله said:

‎”The truth will only be shown to perceptive people who will use the light of their minds to see the consequences of the matters they face."

‎[al-Fawā’id]

لا يألفنّ أحدكم مُصاب أخيه وإن طال
One must not become insensitive to the pains of his brother even if they prolong

ولا يغفلنّ بالدعاء له متى بقي البلاء أو زال
And should not be heedless of making duaa for him; whether the trial is present or gone

Rabī’ bin Khuthaym رحمه الله said to his companions:

“Do you know the disease, the cure, and the recovery?”

They said: “No.”

He said: “The disease is sin, the cure is seeking forgiveness from Allah, and the [pathway to] recovery is to repent and then not repeat it.”

[Bughyat At-Talab: 3/469]

'Alī b. Abī Ṭālib said: “No one should place his hopes in anyone except his Lord.” ‘

{Majmoo’ al-Fataawa of Ibn Taymiyyah (v. 8, p. 99)}

Ibn Rajab رحمه الله said:

إذا لم تستطع أن تنافس الصالحين في أعمالهم ، فنافس المذنبين في استغفارهم

“If you’re unable to compete with the righteous in performing good deeds, then compete with sinners by racing towards forgiveness.”

أستغفر الله العظيم وأتوبُ إليه

Uthman رضي الله عنه once began to stutter during a khutbah and then said,

"I'm not good at giving speeches, but I will learn it, In shaa Allah!"

[(سير الخلفاء الراشدون،) صفحة:٢٩٦]

قل لمن يرجو في الحياةِ خلودًا لستَ يا عافاك الإلهُ سميعا

فلقد قامتِ المنايا على مِنـْـبَرِ وعظٍ ، وأنذرتكَ وقوعا

فتغافلتَ ، ما إخالُكَ إلا عن قليلٍ مباغَتًا وصريعا

Say to one who hopes for eternity in this life: "You, may God grant you wellbeing, do not hear!

For death has stood atop a pulpit of advice And warned you of its occurrence.

Yet you paid no heed—it will not bypass you Except briefly, suddenly felling you."