The Messenger of Allah ﷺ said, "No two Muslims meet and shake hands without being forgiven before they part."
قال رسول الله ﷺ: ما من مسلمين يلتقيان، فيتصافحان إلا غفر لهما قبل أن يفترقا.
This was narrated by Abu Dawud (5212), Tirmidhi (2727), Ibn Majah (3703), and Ahmad (18547), all of them through Ajlah, from Abu Ishaq, from Bara bin Azib, who related it.Tirmidhi said, "This is a gharib hadith from the hadith of Abu Ishaq from Bara, and this hadith has been narrated from Bara through more than one route." In one copy it reads, "hasan gharib."I say, its isnad is hasan, for Ajlah is Ibn Abdullah Kindi, about whom there is disagreement, though his hadith is hasan so long as its error or objectionable content is not evident in the text.Abu Dawud also narrated it (5211) with another isnad from Bara, with the wording, "When two Muslims meet, shake hands, praise Allah , and seek His forgiveness, they will both be forgiven." Its isnad contains an unknown narrator, but each of the two isnads strengthens the other. Perhaps this is the isnad Tirmidhi meant when he said that this hadith has been narrated from Bara through more than one route.