It is to be emphasized on that there is a clear indication in the Qur’an to utter the phrase “in sha’ Allah” upon embarking on a certain act. Such indication was originally directed to the Prophet and to his followers after him until the Day of Judgment. Referring to this, Allah Almighty says: “And say not of anything: Lo! I shall do that tomorrow. Except if Allah will. And remember thy Lord when thou forgettest…” (Al-Kahf: 23-24)
“One of the teachings of Islam is that when we undertake a task, we should start by saying, “in sha’ Allah” —Allah willing. According to the Qur’an, the owners of a certain orchard made it known that they intended to pick its fruits as soon as they were ripe. But they added no reservation such as, “If it be Allah’s Will.” When they reached their orchard the next morning, they found that a calamity sent by Allah had destroyed their entire crop. This was the result of their having omitted to say, “Allah willing.” (Al-Qalam: 17)
“Allah willing” or “in sha’ Allah” is a phrase of great significance. Islam teaches us that whenever a person is going to embark upon any venture, he should say, “If Allah wills” before he begins.
This is to acknowledge the reality that Allah Alone is the Doer in this world. A person can achieve his ends successfully only when Allah’s Blessings are with him. Allah Alone has the power to make things happen, as everything functions according to His Will. Man can only wish for certain happenings, but occurrence rests with Allah Alone.
When man thinks seriously of Allah’s Omnipotence and his own total helplessness, such feelings find expression in the words “in sha’ Allah”.
In this way, he acknowledges that he can only make a beginning. So far as the completion of the task is concerned, it lies entirely in Allah’s Hands. The phrase “in sha’ Allah” in its essence is a form of prayer.
Beginning one’s work with “in sha’ Allah” is like seeking Allah’s company and when Allah, the Lord of the universe, accompanies us on our journey, who can stop us from reaching our destination?”
Dr. Rif`at Fawzi, former professor of Shari`ah at Cairo University, adds: “Originally, it is better to say “in sha’ Allah” before starting the act that one intends to do. It can be said after the end of the act if one forgets to say it at the beginning, but only as a form of blessing or tabarruk.
Also, there is nothing wrong with saying the phrase “in sha’ Allah” in a low or a loud voice, although uttering it in an audible voice may be better.”