Usama b. Zaid said:
When God's messenger became very weak[*] the people and I came down to Medina. I went in to visit God's apostle who was tongue-tied and unable to speak: but he was placing his hands on me and raising them, and I recognised that he was invoking a blessing on me.
*i.e., during his last illness.
Tirmidhi transmitted it, saying this is a gharib tradition.