What is to be said upon performing ablution

بابُ ما يَقولُ على وضُوئه

What is to be said upon performing ablution

Bismillah

It is desirable to say in beginning: Bismillah (in the name of Allah). If a person forgets to recite Tasmiyah in the beginning, it is permissible for him to recite it during ablution. However, if he forgets until his ablution is over, there is nothing against him and his ablution is valid.

Some scholars said: It is desirable for the one who performs ablution to say after Tasmiyah: Ashhadu Alla Ilaha Illah Allah wahdahu La Sharika Lahu Wa Ashhadu Anna Muhammadan `Abduhu war-Rasulullah. (I bear witness that there is no god but Allah alone and I bear witness that Muhammad is His Servant and Messenger. However, this form was not reported from the Prophet (peace be upon him).

A person may say after the end of ablution: Ashhadu Alla Ilaha Illa Allahu Wahdahu La Sharika Lahu Wa Ashhadu Anna Muhammada `Abduhu Warasuluhu, Allahumma Ij`alny Mina At-Tawwabina Waj`alny Mina Al Mutatahirin, Subhanaka Allahumma Wabihamdika Ashhadu Alla Ilaha Illa Anta Astaghfiruka Wa Atubu Ilayk. (I testify that there so no true god except Allah Alone, Who has no partners and that Muhammad (peace be upon him) is His Servant and Messenger. O Allah make me among those who repent and purify themselves. Glory be to You. O Allah, and I begin with praise of You, I testify that there is no god but Thou; I ask Thy pardon, and return to You in repentance.

Ashhadu Alla Ilaha Illa Allahu Wahdahu La Sharika Lahu Wa Ashhadu Anna Muhammadan `Abduhu Warasuluhu Futihat Lahu Abwabu Al Jannati Ath- Thamaniyah Yadkhulu Min Ayyiha Sha'.

I testify that there is none worthy of worship (in truth) but Allah and that Muhammad is the servant of Allah and His Messenger, the eight gates of Paradise would be opened for him and he may enter by whichever of them he wishes .

As for invoking Allah during ablution at washing every organ, it was not reported from the Prophet (peace be upon him).