Sunan Abu Dawud
101
Sahih+2

Narrated AbuHurayrah: The Messenger of Allah (ﷺ) said: The prayer of a person who does not perform ablution is not valid, and the ablution of a person who does not mention the name of Allah (in the beginning) is not valid

SahihAl-Albani
SahihMuhammad Muhyi Al-Din Abdul Hamid