Asking Permission
حَدَّثَنَا عَمْرُو بْنُ عَاصِمٍ، حَدَّثَنَا هَمَّامٌ، عَنْ قَتَادَةَ، قَالَ قُلْتُ لأَنَسٍ أَكَانَتِ الْمُصَافَحَةُ فِي أَصْحَابِ النَّبِيِّ صلى الله عليه وسلم قَالَ نَعَمْ.Narrated Qatada:I asked Anas, "Was it a custom of the companions of the Prophet (ﷺ) to shake hands with one another?" He said, "Yes
From Sahih al-Bukhari, whose reports the scholars accept as authentic.