Is it necessary to say "Bismillah" before rinsing the mouth – may Allah reward you with goodness?

The 'Tasmiyah' (saying Bismillah) in ablution (Wudu') comes immediately after the intention (niyyah) and before washing the hands, rinsing the mouth, and all other acts of Wudu'. It consists of saying: "Bismillah (In the name of Allah)." The majority of scholars hold that it is a recommended Sunnah and not obligatory. The Wudu' of someone who omits it, even intentionally, is valid.