Talha bin Nafi' Abi Sufyan al-Askaf طلحة بن نافع الواسطي أبو سفيان الإسكاف · Chapters on Seeking Permission

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."