The Noble Imām Shaykh Muhammad Ibn Sālih al-‘Uthaymīn (may Allāh have mercy upon him) said:
Allāh has obligated them (i.e. the five daily prayers) upon the servants. When He first obligated them, He obligated them as fifty prayers to be prayed in the day and night. And being that it was fifty prayers, it is an indication of the love of Allāh for them, His care for them and that they are an act of worship which is entitled to take up most of the person’s time because it is the connection between Allāh and His servants. The believer finds within it the ease of himself and the tranquility of his heart. Because of this, it was the coolness of the eyes of the Messenger of Allāh (ﷺ). If the Muslim was to pray fifty prayers and every prayer took up a fourth of an hour (i.e. 15 minutes), he will be in the prayer 12 and a half hours. Therefore, if the person was to preoccupy (himself) in it, it will take up most of his time.
Then there took place between Allāh and His Messenger (ﷺ) a back and forth until Allāh lightened (the prayers) upon His servants by way of His generosity, mercy and virtue, therefore making them five in the performance (of them) and fifty in the scales (of reward). And in these five (daily prayers) are the benefits of the five (daily prayers) and the reward of fifty and this is from the favor of Allāh.
And this is not from the angle of the reward of good is the likes of ten good deed. That’s because for all the righteous actions, the good in it is equal to ten good deeds. Therefore if it (i.e. the reward for the prayers) are from the angle of the good being equivalent to ten good deeds then there would be no difference between it and the other acts of worship. However, these five prayers are as if we prayed fifty prayers and for every prayer is ten good deeds which reaches (the reward of) five hundred good deeds in (the performance of) these five daily prayers. Allāh increases the reward from whomever He wills. This one good deed is counted when performed as if it was performed ten times. As an example, when a person prays the ʿAsr prayer, it is as if he prayed it ten times and the like. Therefore, this is the distinguishing feature being that it is five prayers by way of the performance (of them) and fifty prayers in the scales (of good).”
Source: Ṣifatus-Ṣalāh pg. 16-17
Translated by Abu Yusuf Khaleefah
18th of Muharram, 1437 (11-01-2015)
Masjid Nur Allah, Queens, NYC