It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "When Allah drowned Pharaoh, he said: 'I believe that there is no god except the One in whom the Children of Israel believe.' At that Jibril (peace be upon him) said: 'O Muhammad, if only you had seen me taking the mud of the sea and stuffing it into his mouth, for fear that mercy would reach him.'"
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12876