1- The slave of Allaah cannot actualize 'You are the One that we worship' except with two principles: one of them is following the Messenger and the second is having sincerity (Ikhlaas) for the one worshipped.
Ibn al-Qayyim – ‘Tahdeeb al-Madrij’ 68
2- Sincerity for Allaah is that a person's intent is for Allaah and intends everything for Him, causing fountains of wisdom to spring up from his heart on to his tongue.
Ibn Taymeeyah – 'an-Naboowaat' 147
3- Whenever the sincerity of the slave of Allaah strengthens, his worship becomes more complete.
Ibn Taymeeyah – 'al-Fatawa' 10/198
4- In relation to the amount of Tawheed a slave has for his Lord, and his sincerity for the religion for Allaah is the amount he is deserving of the generosity of Allaah upon him, from intercession and other things.
Ibn Taymeeyah – ‘As-Sarim al-Monkey’ 390
5- A person does not show his actions to the creation, except due to his ignorance of the Greatness of the Creator.
Ibn Rajab – ‘Kalimat ul-Ikhlaas’ 31
6- Ikhlaas cannot be achieved except after having Zuhud, and there is no Zuhud except after having Taqwa, and Taqwa is following the commands (of Allaah and His Messenger) and keeping away from prohibitions.
Ibn Taymeeyah – 'al-Fatawa' 1/94
7- Strive today in implementing Tawheed, since there is nothing that will deliver you to Allaah except Tawheed. Also, be eager in fulfilling its rights, since there is nothing that can save you from the fire except Tawheed.
Ibn Rajab – ‘Kalimat ul-Ikhlaas’ 54
8- Whoever is sincere in regards to the actions of the Deen, which he does for Allaah, then he is from the pious Awliyah of Allaah.
Ibn Taymeeyah – 'al-Fatawa' 1/8
9- If you correct your hidden deeds subsequently Allaah will correct your outward deeds.
Ibn Taymeeyah – 'al-Fatawa' 3/277
10- Having the correct understanding of the Deen is light which Allaah throws into the heart of the slave of Allaah, which is increased by having the Taqwa of Allaah and having good intent.
Ibn al-Qayyim – ‘Ilaam al-Muaq'een' 1/69
11- Ikhlaas is the way to salvation, Islaam is the ship to safety and Emaan is the seal of security.
Ibn al-Qayyim – 'Dar miftah as-Sa'ada' 1/74
12- Certainly the strength of Yusuf's sincerity - alayhi sallam - was stronger than the beauty of Azeez's wife, stronger than her allure, and his want for her.
Ibn Taymeeyah – 'al-Fatawa' 10/602
13 – The heart of the truthful person is filled with the light of truth and he has the light of Emaan.
Ibn al-Qayyim – 'Madarij as-Salikeen' 2/282
14- The sincere person is fortified by Allaah due to his worship of Him Alone, intending his Face Alone. He has humility for Him Alone, and hope in Him Alone, requesting from Him Alone, submissiveness for Him Alone and has a dire need of Him Alone.
Ibn al-Qayyim – 'Madarij as-Salikeen' 2/202
15- There is nothing that drives away the afflictions of this world except Tawheed. That is why the supplication of the distressed person is with Tawheed. Such as, the supplication of Yunus. The distressed person does not supplicate by what Yunus supplicated with except that Allaah releases him from his hardship with Tawheed.
There is nothing more gruesome for the distressed person except shirk, and there is nothing that can rescue you from it except Tawheed, it is the refuge for the creation, its shelter, its fortress and its aid.
Ibn al-Qayyim – 'al-Fawaid' 96
16-The reward is doubled in accordance with one perfecting his Islaam and with his perfecting the strength of Ikhlaas, in that action.
Ibn Rajab – ‘Jama' al-Aloom’ 2/316
17- If a benefit could be achieved from an action performed without Ikhlaas, then Allaah would not have criticised the hypocrites.
Ibn al-Qayyim – 'al-Fawaid' 65
18- Without doubt al-Ikhlaas negates the reason for entering into the Fire, therefore, who ever enters the fire, from those who said: ‘‘la illah ila Allaah’ (there is none worthy of worship except Allaah)’ then this is proof that he never implemented the sincerity of ‘‘la illah ila Allaah’’ which would have prohibited him from the fire.
Ibn Taymeeyah – 'al-Fatawa' 10/261
19 – If the slave of Allaah perfects his Tawheed and his sincerity for Allaah and he establishes / fulfills all its conditions with his heart, and his tongue and his limbs then forgiveness for his past sins becomes obligatory.
Ibn Rajab – ‘Jama' al-Aloom’ 2/417
20 – Fitnah continues upon the heart, except if the Deen of the slave is completely for Allaah.
Ibn Taymeeyah – 'al-Fatawa' 10/545
21- Without doubt, the sincere person has tasted the sweetness of his worship for Allaah, this is what stops him from performing worship for other than Allaah, since there is nothing more sweet or more blessed for the heart than the sweetness of Emaan in Allaah the Lord of the worlds.
Ibn Taymeeyah – 'al-Fatawa' 10/215
22- The different grades of doing actions for Allaah are in relation to what is in the heart from Emaan, sincerity, love and that what follows them.
Ibn al-Qayyim – 'al-Waabil as-Sayib' 22
23- Sincerity is not combined in the heart along with the love of being praised by the people, and being commended by them, and also having greed for what the people have, except like water being combined with fire.
Ibn al-Qayyim – 'al-Fawaid' 267
24- Ikhlaas and Tawheed are a tree in the heart. Its branches are good actions. Its fruits are a good life in this world, and eternal comfort in the Hereafter, and just like in Paradise the fruits whose supply is not cut off, nor are they out of reach, likewise are the fruits of Tawheed and Ikhlaas in this world.
Ibn al-Qayyim – 'al-Fawaid' 292
25- An action done without Ikhlaas and without following the Messenger is like a traveler whose sock becomes filled with sand, which weighs him down, and has no benefit.
Ibn al-Qayyim – 'al-Fawaid' 89
26- Allaah loves from His slave that he beautifies his tongue with the truth, and his heart with Ikhlaas and love, turning repentantly and reliance upon Allaah.
Ibn al-Qayyim – 'al-Fawaid' 327
27- Having sincerity for the Deen of Allaah is the foundation of justice, likewise committing Shirk with Allaah is a great injustice.
Ibn Taymeeyah – 'al-Fatawa' 1/87
From the sayings of the Salaf about Truthfulness and Sincerity
Abdul Wahhab bin Muhammad as-Salafi
Abbas Abu Yahya