مُسْنَدُ أَحْمَدَ
Musnad Ahmad 1611
Musnad Abu Ishaq Sa'd bin Abi Waqqas
It was narrated from Mus"ab bin Sa"d: My father told me: We were sitting with the Messenger of Allah (ﷺ) and he said: "Will one of you be incapable of earning one thousand hasanahs every day?" One of the people sitting with him asked him: O Prophet (ﷺ) of Allah, how could one of us earn one thousand hasanahs? He said: “He says tasbeeh one hundred times, and it will be recorded as one thousand hasanahs[good deeds] or will erase one thousand sayyi"ahs (bad deeds)."
Musnad Ahmad 1612Sahih (Darussalam) [ Muslim (2698}}