“(Those whose hearts are tranquil are) those who bear in mind that they will indeed meet their Rabb and that indeed to Him they will return.” (Surah Baqarah, 46)
Now understand that experience has proven that if a person wishes to empty his minds of the myriad of thoughts and host of worries in it, this is virtually impossible. There is only one solution, and that is since the mind cannot concentrate on two things at the same time, if its concentration is directed to one objective then all other thoughts and worries will automatically recede into oblivion. Therefore, after mentioning concentration, the meditation is stated by virtue of which other thoughts will be cut off and their severing will bring the heart’s/mind’s impulses to a rest; this rest will bring tranquillity to the heart/mind; this tranquillity in turn will make Salaat easy and this ease will stimulate one to perform Salaat punctually.
Thinking of “they will indeed meet their Rabb” they understand that their reward for their Salaat will be handsomely conferred then, and thinking of “to Him they will return” they understand that they have to account for their actions. The first thought produces eagerness, whilst the second produces vigilance.
Firstly, meditating any praiseworthy thought brings the mind to concentrate on a virtuous deed. Thoughts which produce eagerness and vigilance are particularly effective, however, in preparing and propelling towards virtuous deeds. (Bayaanul Qur’aan)