Dua Before Wudu (Ablution)
بِسْمِ اللَّهِ
Bismillah.
"In the name of Allah."
Sunan Abi Dawud 101
Spiritual Benefits
The Prophet (PBUH) stated that there is no perfect wudu for the one who does not mention the name of Allah before it.
When Should I Say This Dua?
Say this right before you begin washing your hands to start wudu.
Proper Etiquette (Sunnah)
Ensure you are making the intention (niyyah) for purification along with reciting this.