It is narrated from Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "When a man comes to visit a sick person, let him say: O Allah, heal Your servant so-and-so; he will wound an enemy for You, or walk to a prayer for Your sake."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13704