Umayr bin Ishaq narrates that Sayyiduna Abu Hurayrah (may Allah be pleased with him) met Sayyiduna al-Hasan bin Ali (may Allah be pleased with them both) and said: "Lift your garment so that I may kiss the place where I saw the Prophet (peace and blessings be upon him) kiss." So he lifted the garment from his belly, and Sayyiduna Abu Hurayrah (may Allah be pleased with him) placed his hand on his navel.
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 2567