تَقَرُّبُ العَبدِ إلَى اللَّهِ سبحانَهُ بِإخلاصِ نِيَّتِهِ . ح: 4477
The servant can come near to Allah, glory be to Him, by making his intentions sincere. H: 4477
علَيكُم بِصِدقِ الإخلاصِ وحُسنِ اليَقينِ ، فإنّهُما أفضَلُ عِبادَةِ المُقَرَّبينَ . ح: 6159
Observe true sincerity and excellent certainty, for they are both the best form of worship [carried out] by those brought near [to Allah]. H: 6159