Musnad Ahmad 30:2119

Musa ibn Dawud narrated to us, he said: Ibn Lahi'ah narrated to us, from Ubayd Allah ibn Abi Ja'far, from Sa'id ibn Abi Sa'id, from his father, from Abu Hurayrah, from the Prophet, may Allah bless him and grant him peace: "From Allah, the Almighty and Majestic, that He said: 'I became ill, and the son of Adam did not visit Me. And I became thirsty, and the son of Adam did not give Me to drink.' I said: 'Do You become ill, O Lord?' He said: 'A servant of My servants, who is on the earth, becomes ill, and he is not visited. If he had visited him, he would have found that which he visited to be for Me. And he becomes thirsty on the earth, and he is not given to drink. If he had given him to drink, he would have found that which he gave him to drink to be for Me.'"