that the Prophet (ﷺ) said: "taking hold of the hand is from the completeness of the greeting."
Jami` at-Tirmidhi Book 42, Hadith 43
← Previous Hadith that he asked Anas bin Malik: "Did the Companions of the Messenger of Allah (ﷺ) use to shake each other's hand?" He said, "Yes."

Jami` at-Tirmidhi Book 42, Hadith 42 Next Hadith → that the Messenger of Allah (ﷺ) said: "From the complete of visiting the ill is that one of you place his hand on his forehead" - or he said - "on his hand, and ask him how he is. And shaking hands completes your greetings among each other."

Jami` at-Tirmidhi Book 42, Hadith 44