Hadith 6965
Umair bin Ishaq narrates: I was walking with Sayyiduna Imam Hasan bin Ali (may Allah be pleased with him) on a road in Madinah Munawwarah when we met Sayyiduna Abu Hurairah (may Allah be pleased with him). He said to Sayyiduna Imam Hasan (may Allah be pleased with him): Please lift the cloth from your stomach and allow me to sacrifice myself for you, so that I may kiss the place where I saw the Noble Prophet (peace and blessings be upon him) kiss. The narrator says: So he lifted the cloth from his stomach and Sayyiduna Abu Hurairah (may Allah be pleased with him) kissed his navel.
(The narrator says:) If the navel had been included in the area of covering ('awrah), then Sayyiduna Imam Hasan (may Allah be pleased with him) would not have lifted the cloth from it.