However, if a person swears an oath upon Allah out of confidence in His grace and hopeful expectation of His bounty, this is permissible, as the Prophet ﷺ said: “Among the servants of Allah are those who, were they to swear an oath upon Allah, He would fulfil it for them.”

The report of Jundub further highlights the danger of the tongue and the necessity of guarding it. Muʿādh (may Allah be pleased with him) related: “I asked, ‘Messenger of Allah, will we really be held accountable for what we say?’ He replied, ‘May your mother be bereaved of you, Muʿādh! Are people flung on their faces—or he said, on their nostrils—into the Fire for anything other than the harvest of their tongues?’” Recorded by al-Tirmidhī, who declared it authentic.

From the foregoing it is clear that one must be vigilant in speech and avoid any wording that shows poor manners toward Allah, exalted is He, for such expressions impair one’s creed and diminish tawḥīd (affirming the divine oneness). Thus it is wrong to say, “Peace be upon Allah,” because He Himself is as-Salām (the Source of Peace), and extending peace is a supplication offered to someone; Allah is the One Who is supplicated. Likewise one should not say, “O Allah, forgive me and have mercy on me, if You will,” or similar phrases. Every supplication must be made with firm resolve, without attaching it to “if You will,” for Allah does whatever He wills and none can compel Him.

Nor is it permissible to swear an oath upon Allah forbidding Him to show mercy to, or forgive, a particular person, for that would be to restrict His mercy and to think ill of Him. Similarly, one must not say, “What Allah and so-and-so willed,” for the conjunction “and” implies partnership, and no one shares with Allah—glorified be He—any affair whatsoever. Instead, one should say, “What Allah willed, then so-and-so willed,” because the use of thumma (“then”) denotes sequence and dependence: the creature’s will follows and is subject to the will of Allah, not coequal with it.

All of this impresses upon the Muslim the obligation to study sound creed and to know what affirms it and what undermines it, so that he may proceed with clear insight and not fall into error unawares. May Allah grant everyone beneficial knowledge and righteous deeds.