Imām Ibn al-Qayyim [d. 751 AH] said: As for the saying of some people [when advised to abandon sin]: ‘I will not leave that which I have certainty in [this dunyā] for that which I am doubtful concerning [the ākhirah].’ It should be said to them: either you are doubtful concerning the promise of Allāh’s reward, punishment, and the truthfulness of His messengers, or you have certainty regarding [the nature of these things]. If you have certainty regarding them, then know that you have only abandoned a small, short-lived, transient, rapidly fading morsel [of enjoyment] for a very short [time], in exchange for a matter in which there is no doubt, nor end.

However, if you are in doubt [concerning these matters] then reacquaint yourself with the signs of your Lord the Most High. For these signs prove His existence, His ability, His will, and His Oneness.

They show the truthfulness of His messengers in what they have related to us concerning Him. Detach yourself [from this dunyā], and stand as an onlooker or debator before Allāh Himself until it becomes clear to you that the messengers of Allāh have brought only the truth in which there can be absolutely no doubt. Truly, the Creator of this world and the Lord of the heavens and the earth is above, exalted, and far-removed from ever [being in a state] that is contrary to that which His messengers have related concerning Him. Whomsoever attempts to ascribe to him other than that indeed tries to insult Him, label Him a liar, and has objected to His Lordship, and complete sovereignty. For it is impossible and completely incomprehensible for any individual with an undisturbed constitution to fathom that the true Owner [of everything in existence] could ever be disabled or ignorant. Or that He knows absolutely nothing; lacking the ability to hear, see, or speak. Or that He does not order or forbid, or reward or punish, or honour or humble whomever He wills. Or that He does not send messengers to the farthest reaches and to every obscure location within His kingdom. Neither does He possess any sort of attention towards His creation; rather that He should leave them purposeless, or abandon them to wander aimlessly. [To postulate such an idea] would be an insult to the most random of human kings and would be considered a preposterous supposition. How then could such a thing ever be ascribed to the True King, the Perfect in Justice, the Manifest Truth [Allāh]?

Source: Al-Dāʾ wa al-Dawāʾ: 81-82
Translated by: Riyāḍ al-Kanadī