A pronoun is a word that can be used instead of a noun. So in order not to be repeating the noun or repeating the appearance of a noun, a pronoun is used.
The unchanging God is the only blank source of true peace but all of Manson has done a blank part to separate man from Him"
God is a noun in the sentence and is repeated twice. The second appearance of "God" can be replaced by the pronoun "Him".
