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.
Sunan Abi Dawud Book 1, Hadith 101
← Previous Hadith The Messenger of Allah (ﷺ) came upon us. We brought water for him in a brass vessel and he performed ablution.

Sunan Abi Dawud Book 1, Hadith 100 Next Hadith → This tradition means that if a person performs ablution and takes a bath but does not have the intention to perform ablution for prayer and purify himself from sexual defilement, his ablution or bath is not valid.

Sunan Abi Dawud Book 1, Hadith 102