Bismilla: In the Name of Allah azza wa Jal

Bismillah before Wahi

In Ad-Durrul Manthur, Ibn Umar RA is reported as saying that surely, whenever Jibreel AS used to bring Wahi to Rasulullah SAW, he used to first recite:
Bismillah-rahmanir-rahim(In the name of Allah,the most Gracious, the most Merciful)
The reason for the above is as follows: in Bismillah there are 3 names of Allah SWT:
1) Allah SWT which is Allah's own name indicating that all projects can only be initiated by the will of ALLAH SWT.
2) Rahman (kind) which is his attributive name indicating that only Allah SWT can keep that project intact and existent (guarding it against destruction).
3) Rahim (Most Merciful) which is also his attribute name indicating that only Allah SWT can, through his mercy and grace, enable any person to derive benefit from that project.
This clearly proves that any action beginning with: Bismillah-rahmanir-rahim(In the name of Allah,the most Gracious, the most Merciful) Will be granted barakah (blessings) from the beginning till end

Bismillah before doing anything

It is for this reason that Rasulullah SAW used to recite: Bismillahir-rahmanir-rahim(In the name of Allah, the most Gracious, the most Merciful.) before doing any work.He SAW also advised the Ummah to do the same. For example, reading it before shutting the door, before putting out the light, before taking meals, before drinking water, before boarding any mode of transport

The Beauty of Islam
Islam is not confined only to the masjid and madrasah.It is a way of life. each and every aspect of a muslim's life is supposed to be deen. It is for this reason that Rasulullah SAW has shown the ummah simple little methods which would render each and every world affair of his to become deen and for which he will be rewarded. It is for this reason that saying: Bismillahir-Rahmanir-Rahim(In the name of Allah ,the most Gracious, the most Merciful.) before any action, will render that action into an ibadah for which the reader will be rewarded. Besides by saying: Bismillahir-Rahmanir-Rahim (In the name of Allah ,the most Gracious, the most Merciful.) before any action, one is suggesting that his every affair-weather small or big- can only be accomplished with the help and mercy of Allah SWT.

Bismillahir-Rahmanir-Rahim( In the name of Allah ,the most Gracious, the most Merciful.) Therefore every activity of a person will become ibadah.By doing this, he will draw closer to Allah SWT and distance himself from the accursed shaytan (devil).And by not doing this he will deprive none other than himself.

According to Ibn Abbas RA in Ad-Durrul Manthur, rasulullah SAW has said that people are unaware of the blessings of one ayah of the Holy Qur'an which was revealed to no one other than me and Sulaiman AS.