Riyad as-Salihin 1843

'Asim Al-Ahwal said:

'Abdullah bin Sarjis (May Allah be pleased with him) said to the Messenger of Allah (ﷺ): "O Messenger of Allah! May Allah forgive all your sins!" The Messenger of Allah (ﷺ) said, "And yours also." 'Asim reported: I asked 'Abdullah: "Did the Messenger of Allah (ﷺ) seek forgiveness for you?" He replied: "Yes, and for you also." Then he recited the Verse: "Seek forgiveness for your sins and for the believing men and the believing women." (47:19)

[Muslim].