It is narrated through the same chain that the Messenger of Allah (peace and blessings be upon him) said to Sayyiduna Ali (may Allah be pleased with him): "The first four people to enter Paradise will be: I, you, Hasan and Husayn. Our offspring will be behind us, our wives behind our offspring, and our followers on our right and on our left."
Hadith Referenceالمعجم الكبير للطبراني / باب الألف / 946