As for the effects of certainty upon the heart, they are its serenity and reassurance. Abraham said, “but so that my heart may be at ease” (al-Baqarah 2:260), and the Prophet ﷺ said, “Righteousness is that which the heart finds tranquillity in” (1); in another wording: “Truthfulness is that which the heart finds tranquillity in” (2). When a servant attains the station of certainty in his knowledge, his heart becomes tranquil concerning every tenet of faith. It is likewise at peace with the realities and spiritual states of faith, all of which revolve around love of Allah and remembrance of Him, the two being inseparable. Allah the Exalted says, “Truly, in the remembrance of Allah do hearts find rest” (ar-Raʿd 13:28).

Thus, when the divine reports reach the heart, it settles; no doubt or hesitation remains about anything Allah has related in His Book or on the tongue of His Messenger. Rather, the heart rejoices in them, confident that this is the greatest benefit it could ever receive.

The heart is also at ease with regard to commands and prohibitions: it completes what is commanded, shuns what is forbidden, hopes for Allah’s reward, and trusts in His promise.

It likewise rests in the face of calamities and disliked events, meeting them with an open breast and the hope of reward. Knowing that they come from Allah, the servant is pleased and submits; the burden therefore feels light and its weight becomes easy to bear.

From this the bodily effects of certainty are understood, for outward actions are built upon the actions of the heart. Consequently, the people of certainty are the most perfect of creation in every praiseworthy trait, for certainty is the very spirit that gives life to deeds and character and carries them. Allah alone grants success and bestows both certainty and the means that lead to it.