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."
أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ تَمَامُ عِيَادَةِ الْمَرِيضِ أَنْ يَضَعَ أَحَدُكُمْ يَدَهُ عَلَى جَبْهَتِهِ أَوْ قَالَ عَلَى يَدِهِ فَيَسْأَلَهُ كَيْفَ هُوَ وَتَمَامُ تَحِيَّاتِكُمْ بَيْنَكُمُ الْمُصَافَحَةُ