Except [when adding], “If Allah wills.” And remember your Lord when you forget [it] and say, “Perhaps my Lord will guide me to what is nearer than this to right conduct.”
Chapter 18 Al-Kahf : Verses 23-24
Saying “If Allah wills” when determining to do Something in the Future
Here Allah, may He be glorified, shows His Messenger the correct etiquette when determining to do something in the future; this should always be referred to the will of Allah, the Knower of the Unseen, Who knows what was and what is yet to be and what is not to be, and how it will be if it is to be. It was recorded in the Two Sahihs that Abu Hurayrah said that the Messenger of Allah said:
(Sulayman bin Dawud (peace be upon them both) said: “Tonight I will go around to seventy women ﴿according to some reports, it was ninety or one hundred women﴾ so that each one of them will give birth to a son who will fight for the sake of Allah.” It was said to him, ﴿according to one report, the angel said to him﴾ “Say: `If Allah wills'”, but he did not say it. He went around to the women but none of them gave birth except for one who gave birth to a half-formed child.) The Messenger of Allah said, (By the One in Whose hand is my soul, had he said, “If Allah wills,” he would not have broken his oath, and that would have helped him to attain what he wanted. ) According to another report, (They would all have fought as horsemen in the cause of Allah.) At the beginning of this Surah we discussed the reason why this Ayah was revealed: when the Prophet was asked about the story of the people of the Cave, he said, “I will tell you tomorrow.” Then the revelation was delayed for fifteen days. Since we discussed this at length at the beginning of the Surah, there is no need to repeat it here.
(And remember your Lord when you forget) It was said that this means, if you forget to say “If Allah wills”, then say it when you remember. This was the view of Abu Al-`Aliyah and Al-Hasan Al-Basri. Hushaym reported from Al-A`mash from Mujahid that concerning a man who swears an oath, Ibn `Abbas said “He may say `If Allah wills’ even if it is a year later.” Ibn `Abbas used to interpret this Ayah:
(And remember your Lord when you forget) in this way. Al-A`mash was asked, “Did you hear this from Mujahid” He said, “Layth bin Abi Salim told it to me.” The meaning of Ibn `Abbas’ view, that a person may say “If Allah wills”, even if it is a year later, is that if he forgets to say it when he makes the oath or when he speaks, and he remembers it later, even a year later, the Sunnah is that he should say it, so that he will still be following the Sunnah of saying “If Allah wills”, even if that is after breaking his oath. This was also the view of Ibn Jarir, but he stated that this does not make up for breaking the oath or mean that one is no longer obliged to offer expiation. What Ibn Jarir said is correct, and it is more appropriate to understand the words of Ibn Abbas in this way. And Allah knows best.
(And never say of anything, “I shall do such and such thing tomorrow.” Except (with the saying), “If Allah wills!” And remember your Lord when you forget) At-Tabarani recorded that Ibn `Abbas said that this meant saying, “If Allah wills.”
(and say: “It may be that my Lord guides me to a nearer way of truth than this.”) meaning, `if you (O Prophet) are asked about something you know nothing about, ask Allah about it, and turn to Him so that He may guide you to what is right.’ And Allah knows best.