For the sake of the Holy Prophet (Sallallahu alaihi wa sallam) Allah (Subhanahu wa Ta’ala) has graced this Ummah with His boundless mercy and benevolence. The Ummah of the past Prophets had very strict rules to get their sins forgiven, to the extent that when Bani Israil prayed to the calf, they were ordered. It is given in the Holy Quran:
And remember Moses said to his people: "O my people! Ye have indeed wronged yourselves by your worship of the calf so turn (in repentance) to your Maker and slay yourselves (the wrong-doers); that will be better for you in the sight of your Maker." Then He turned toward you (in forgiveness); for He is Oft-returning Most Merciful.
(Surah Al Baqarah (2:54))
On the other hand, the Holy Prophet (Sallallahu alaihi wa sallam) told us: Say: "O my Servants who have transgressed against their souls! Despair not of the Mercy of Allah: for Allah forgives all sins:
for He is Oft-Forgiving, Most Merciful. (Surah Zumar (39:53))
Allah's (Subhanahu wa Ta’ala) mercy is forever raining on us, but especially for the sake of the sinful worshippers, Allah (Subhanahu wa Ta’ala) has fixed some special days and nights for forgiveness of sins and pardon.
The Holy Prophet (Sallallahu alaihi wa sallam) is forever worried about His Ummah; day and night He keeps praying to Allah (Subhanahu wa Ta’ala) to forgive and pardon His Ummah. Allah (Subhanahu wa Ta’ala) too wants to see His Beloved Prophet (Sallallahu alaihi wa sallam) pleased and happy, so for the sake of the Holy Prophet (Sallallahu alaihi wa sallam), in the last portion of every night He graces the sky of this world (Aasmaan e Dunya) with His presence and grants the treasures of forgiveness, deliverance and success to His worshippers. Only His favorite worshippers benefit from these blessings. As Allah (Subhanahu wa Ta’ala) says: