بِسمَ اللَّهِ الرَّحمَن الرَّحِيم
Every good action or deed should be started by reciting Bismillah
Below are quoted some Authentic Traditions of Rasulullah (salAllahu alayhi wasalam) regarding Bismillah -In the name of Allah
Saying Bismillah Is Recommended Before Eating
Rasulullah (salAllahu alayhi wasalam) said, "Say Bismillah, eat with your right hand and eat what is in front of you."
Bukhari 7/88, Muslim 2/207, Ahmad 17/92, Muwatta Malik 10/32 and Ibn Majah 1/557
Say Bismillah When Drinking Water
Ibn Abbas (radiAllahu anhu) reported that Rasulullah (salAllahu alayhi wasalam) said, "Do not drink in one gulp like a camel, but in two or three Gulps. Mention the Name of Allah when you start drinking and praise Him after you have finished (Drinking).''
Fath al-Bari 12/197 and Al-Tirmidhi
At The Beginning Of Wudu (Ablution)
Rasulullah (salAllahu alayhi wasalam) said, "Make Wudu Ablution in the name of Allah" An-Nasai 1/11 and Ibn Khuzaimah 1/84
Rasulullah (salAllahu alayhi wasalam) said, "If anyone of you when having intercourse with his wife, says: In the name of Allah. O, Allah! Protect us from Satan and also protect what you grant us (i.e., coming offspring) from Satan; if it is destined that they should have a child, then Satan willnever be able to harm him."
Sahih Bukhari 7/94 and Sahih Muslim 2/1058
When Entering The House
Jabir (radiAllahu anhu) said: I heard Rasulullah (salAllahu alayhi wasalam) saying, "If a person mentions the Name of Allah upon entering his house or eating, Satan says, addressing his followers: `You will find nowhere to spend the night and no dinner.' But if he enters without mentioning the Name of Allah, Satan says (To his followers); 'You have found (A place) to spend the night in, and if he does not mention the Name of Allah at the time of eating, Satan says: `You have found (A place) to spend the night in as well as food."
Sahih Muslim 2/206
When Leaving The House
Rasulullah (salAllahu alayhi wasalam) said, "If anyone of you when leaving the house say In the name of Allah, I trust in Allah, there is no power and might except Allah. Your needs shall be fulfilled, you shall be saved from difficulties and hardships. Shaitaan hearing these words leaves him."
When Slaughtering An Animal
Anas (radiAllahu anhu) reported that Rasulullah (salAllahu alayhi wasalam) sacrificed two horned rams of white color with black markings over them. He also stated: I saw him offering them with his own hand and saw him placing his foot on their sides, and recited in the name of Allah and Glorified Him (Bismillah Allahu Akbar)
Sahih al-Bukhari 7/133, Muslim 2/181, Abu Dawud 3/230, An-Nasai 7/231, Al-Trimidhi 5/76, Ibn Majah 2120
When Fighting For The Cause Of Allah
Rasulullah (salAllahu alayhi wasalam) said, "Fight in the name of Allah and in the way of Allah"
Sahih Muslim 2/69
Before Entering The Toilet
Rasulullah (salAllahu alayhi wasalam) said "When you enter the toilet you should say, In the Name of Allah, I seek protection in you from unclean spirits, male and female."
Abu Dawud 4/264, Ahmad 2/389 and Fath Al-Bari 1/254
Recommended Because It Causes Humiliation To The Shaitan
Abul Malih (radiAllahu anhu) said: I was riding on a mount behind Rasulullah (salAllahu alayhi wasalam). It stumbled. Thereupon I said: May the devil perish! He said: Do not say: May the devil perish! For if you say that, he will swell so much so that he will be like a house, and say: By my power. But say Bismillah for when you say that, he will diminish so much so that he will be like a fly. An-Nasai 6/142, Ahmad 5/59 and Abu Dawud 4946
Recommended When Night Falls
Rasulullah (salAllahu alayhi wasalam) said, "When night falls stop your children from going out, for the devils spread out at that time. But when an hour of the night has passed, release them, close the doors, and mention Allah's Name, for Satan does not open a closed door. Tie the mouth of your water skin and mention Allah's Name; cover your containers and utensils and mention Allah's Name. Cover them even by placing something across it, and extinguish your lamps "
Sahih al-Bukhari 7/527 and Abu Dawud 3722
When Placing The Body Of The Deceased In The Grave
Rasulullah (salAllahu alayhi wasalam) said, "When you are lowering the deceased in the grave you should say In the name of Allah and in accordance to the Sunnah of Rasulullah."
Ahmad 8/58 and Al-Hakim 1/366
The Virtues Of Saying Bismillah
Uthman bin Abu al-As Al-Thaqafi (radiAllahu anhu) reported that he made a complaint of pain to Rasulullah (salAllahu alayhi wasalam) that he felt in his body at the time he had become Muslim. Thereupon Rasulullah (salAllahu alayhi wasalam) said: Place your hand at the place where you feel pain in your body and say in the name of Allah three times and seven times I seek refuge with Allah and with His Power from the evil that I find and that I fear.
When Writing A Letter Bismillah Should Also Be Written:
Abu Sufyan (radiAllahu anhu) said that the contents of the letter were as follows: "In the name of Allah the Most Gracious, the Most Merciful, (This letter is) from Muhammad the slave of Allah and His Apostle to Heraclius the ruler of Byzantine. Peace be upon him, who follows the right path. Furthermore I invite you to Islam, and if you become a Muslim you will be safe, and Allah will double your reward, and if you reject this invitation of Islam you will be committing a sin by misguiding your peasants."
Bukhari 4/191, Muslim 2/91, Al-Trimidhi 7/500
Queen Sheba said O chief! Surely an honorable letter has been delivered to me Surely it is from Sulaiman, and surely it is in the name of Allah, the Most Gracious, the Most Merciful;
Al-Quran, Surah Al-Naml, Ayahs 29-30