Sayyiduna Ali (may Allah be pleased with him) narrates: The Messenger of Allah (peace and blessings be upon him) visited us and spent the night with us while Hasan and Husayn were asleep. Hasan asked for water, so the Messenger of Allah (peace and blessings be upon him) got up and went to a waterskin of ours and began squeezing it into a cup, then came to give him a drink. He handed it to Sayyiduna Hasan; Sayyiduna Husayn also reached out to drink, but he held him back and began with Hasan. Sayyidah Fatimah said: O Messenger of Allah, it is as if he is the dearer of the two to you. He (peace and blessings be upon him) said: "He asked for water first." Then the Messenger of Allah (peace and blessings be upon him) said: "Indeed I and these two (and I think he said: and this sleeping one, meaning Ali) will be in one place on the Day of Resurrection."
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 2609