This booklet is based on The sayings of the Salaf about Truthfulness and Sincerity, compiled by Abdul Wahhab bin Muhammad as-Salafi
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
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