Hadith on Tawhid: Best deed to declare no God but Allah

Abu Dharr reported: I said, “O Messenger of Allah, instruct me.” The Prophet, peace and blessings be upon him, said, “If you do a bad deed, follow it with a good deed to wipe it out.” I said, “O Messenger of Allah, is it a good deed to declare there is no God but Allah?” The Prophet said, “It is among the best of good deeds.

Source: Musnad Aḥmad 21487

Grade: Hasan (fair) according to Ibn Hajar

عَنْ أَبِي ذَرٍّ قَالَ قُلْتُ يَا رَسُولَ اللَّهِ أَوْصِنِي فَقَالَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذَا عَمِلْتَ سَيِّئَةً فَأَتْبِعْهَا حَسَنَةً تَمْحُهَا قُلْتُ يَا رَسُولَ اللَّهِ أَمِنْ الْحَسَنَاتِ لَا إِلَهَ إِلَّا اللَّهُ قَالَ هِيَ أَفْضَلُ الْحَسَنَاتِ

21487 مسند أحمد

129 المحدث ابن حجر العسقلاني خلاصة حكم المحدث حسن في الأمالي المطلقة