Musannaf Ibn Abi Shayba 1:2099

Abu Bakr narrated to us, he said: Waki’ narrated to us, from al-Rabi’, from al-Hasan, regarding a man who performs ablution and his ablution dries: He said: If he was in the process of performing the ablution, he should wash his feet. And if he was not in the process of performing the ablution, he should restart the ablution.