Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: I saw the Messenger of Allah (peace and blessings be upon him) part the thighs of Sayyiduna Husayn (may Allah be pleased with him) (in his childhood) and kiss his zabibah (the tip of his private part).
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12561