Hawzah News Agency – Imam al-Baqir peace be upon him says:

يَجِبُ لِلمُؤمِنِ عَلَى المُؤمِنِ أن يَستُرَ عَلَيهِ سَبعينَ كَبيرَة.

‘It is the duty of a believer towards a fellow believer to conceal seventy of his grave sins!’

Source: al-Kafi, v. 2, p. 207, no. 8