Musannaf Ibn Abi Shayba 21:776

Abu Abd al-Rahman al-Muqri narrated to us, from Sa'id ibn Abi Ayyub, who said: Zahra ibn Ma'bad Abu Aqil narrated to me, that a cousin of his informed him that he heard Uqbah ibn Amir saying: The Messenger of Allah (may Allah bless him and grant him peace) said: "Whoever performs wudu and perfects his wudu, then raises his head toward the sky and says: 'I bear witness that there is no god but Allah alone, He has no partner, and that Muhammad is His servant and His messenger,' the eight gates of Paradise will be opened for him; he may enter through whichever of them he wishes."