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.
Hadith Referenceصحیح ابن حبان / كتاب إخباره ﷺ عن مناقب الصحابة رجالهم ونسائهم بذكر أسمائهم رضوان الله عليهم أجمعين / 6965
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيضعيف - مضى (5566). تنبيه!! رقم (5566) = (5593) من «طبعة المؤسسة». - مدخل بيانات الشاملة -.فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده صحيح