Musannaf Ibn Abi Shayba 3:1947

Hushaym narrated to us, he said: Mughira informed us, from Ibrahim, who said: If he hears it while he is not in a state of ablution, then let him perform ablution, then let him recite it, then let him prostrate. If he does not know it well, let him recite another [verse] instead of it, then let him prostrate.