How sound is the hadeeth “Seek seventy excuses for your brother”?

I do not know of any basis for it. What is prescribed for the believer is to respect his brother if he apologizes to him and accept his excuse if possible, and to think positively of him whenever possible, in hopes that hearts will be free from resentment and that people will be brought together and will cooperate in doing good. It was narrated from ‘Umar (may Allah be pleased with him) that he said: “Do not think badly of a word uttered by your brother, when you can find a good interpretation for it.” end quote.