It is Sunnah for a Muslim to recite ‘Bismillahirrahmanirrahim’ when they wish to begin a good deed/action, and to recite ‘Alhamdulillah’ at the end, in order for the deed to start and finish with beneficence and Barakah.
The first word written by the Qalam (pen) in LawhMahfuz was Basmalah, and the first word revealed to Adam (a.s.) was Basmalah.
Ibn Abbas (r.anhuma) said: “There are many people who when they recite ‘Bismillahirrahmanirrahim’ that Allah (s.w.t) writes for them four thousand Thawab, elevates them by four thousand ranks and erases four thousand sins.”
When a teacher teaches a child ‘Bismillahirrahmanirrahim’ Allah (s.w.t) blesses the child, its parents and the teacher with a pardon from Jahannam.
One day, when Isa (a.s.) was walking by a cemetery, he saw the wrath angels, punishing a person. A while later when he walked by the same cemetery he saw the mercy angels offering the person gifts off a plate from Jannah. He was astonished by this, he prayed two Rak’ah Salah and made Dua to Allah, Allah (s.w.t) revealed to him: “O Isa! That was a sinful man. When he died, his pregnant wife gave birth to their child and educated him. When he grew up, she sent him to a religious teacher. The teacher taught him how to say ‘Bismillahirrahmanirrahim’ The boy learnt this and repeated it. I do not see it right to punish a man under the earth while his son recites my name on the earth. That is why I sent the mercy angels, and they offered him gifts from the plates of Jannah.”