All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
If you are certain that you are in a state of ablution, then you should answer: “Yes.” However, if you say “If Allaah so wills”, this is an answer which is not appropriate to the question and the questioner does not benefit anything from its meaning. Saying “If Allaah so wills” is said in regard to things that will happen in the future and not to things that already happened in the past. Allaah Says (what means): {And never say of anything, “Indeed, I will do such and such thing tomorrow.”, Except [when adding], “If Allaah wills.”}[Quran 18:23-24]. As regards the things that had already happened in the past, it is not permissible to condition them on Allaah’s Will, as this is idle talk, because what happened did not happen except with His Will, because if He had not so willed, it would not have happened.
Allaah Knows best.