Ja’far ibn Muhammad, may Allah have mercy on him, said:

إِذَا بَلَغَكَ عَنْ أَخِيكَ الشَّيْءُ تُنْكِرُهُ فَالْتَمِسْ لَهُ عُذْرًا وَاحِدًا إِلَى سَبْعِينَ عُذْرًا فَإِنْ أَصَبْتَهُ وَإِلا قُلْ لَعَلَّ لَهُ عُذْرًا لا أَعْرِفُهُ

If you hear something from your brother that you reject, then make an excuse for him up to seventy excuses. If you cannot do it, then say: Perhaps he has an excuse I do not know.

Source: Shu’ab al-Iman 7853