Is this Hadith authentic: "Seek seventy excuses for your brother"?

There is no origin for the saying. What is prescribed for the believer is to respect his brother, accept his excuse if possible, and think well of him, out of concern for the soundness of hearts, the unity of word, and cooperation in good deeds. It was narrated from 'Umar, may Allah be pleased with him, that he said: "Do not think ill of a word uttered by your brother when you can find a good interpretation for it."