Seal of Prophets Syedna Muhammad Salla'l la ho alaye hi wasallam is light ---(proof from Quran)

O people of the Scripture (Jews and Christians)! Now has come to you Our Messenger (Muhammad SAW) explaining to you much of that which you used to hide from the Scripture and pass over (i.e. leaving out without explaining) much. Indeed, there has come to you from Allâh a light (Prophet Muhammad SAW ) and a plain Book (this Qur'ân).

Al maeda 15