Musannaf Ibn Abi Shayba 3:5656

Sharik narrated to us, from Ibn Ishaq, from al-Harith, from Ali, who said: The person in a state of major ritual impurity (junub) waits until the end of the time [for prayer]. If he finds water, he performs ablution (wudu), and if he does not find water, he performs dry ablution (tayammum) and prays. If he finds water afterwards, he performs the full bath (ghusl) and does not repeat the prayer.