He passed by Umar bin Khattab, who said, "What an excellent young man Ghudayf is."Then Abu Dharr met him and said, "My brother, ask forgiveness for me."He replied, "You are a companion of the Messenger of Allah, and you are more worthy to ask forgiveness for me!"Abu Dharr said, "I heard Umar bin Khattab say, 'What an excellent young man Ghudayf is,' and the Messenger of Allah ﷺ said, 'Allah has placed truth upon Umar's tongue and heart.'"
أنه مر بعمر بن الخطاب، فقال: نعم الفتى غضيف، فلقيه أبو ذر، فقال: أي أخي استغفر لي، قال: أنت صاحب رسول الله وأنت أحق أن تستغفر لي! فقال: إني سمعت عمر بن الخطاب يقول: نعم الفتى غضيف، وقد قال رسول الله ﷺ: إن الله ضرب بالحق على لسان عمر وقلبه.
Narrated by Abu Dawud (2962), Ibn Majah (108), and Ahmad (21295, 21457), and this last wording is his, and Hakim graded it sahih (3/87). All of them narrated it through various routes from Ghudayf bin Harith, who related it. Some of them did not mention the story. Its chain of transmission is sahih.