Fiqh-us-Sunnah Volume 1, Purification and Prayer, Fiqh 1.029.

Section : Mentioning the name of Allah at the beginning.

There are some weak hadith that mention this act, and all of the chains of these hadith point to the fact that there is some basis for this act. In any case, it is a good act in and of itself and, in general, it is part of the Islamic law.