Sayyiduna Amr bin al-As (may Allah be pleased with him) said: On a cold night during the expedition of Dhat al-Salasil I had a wet dream, and I feared that if I took a ritual bath I would die, so I performed tayammum and then led my companions in the Fajr prayer. They mentioned this to the Prophet (peace and blessings be upon him), and he (peace and blessings be upon him) said: "O Amr, did you lead your companions in prayer while you were junub?" I told him (peace and blessings be upon him) the reason that had prevented me from taking a ritual bath, and I said: I have heard Allah Almighty say: "And do not kill yourselves; indeed Allah is ever Merciful to you" [Surah al-Nisa': 29]. The Messenger of Allah (peace and blessings be upon him) laughed and did not say anything.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1070