Luke 1: knowledge of salvation

We read about the birth of John Baptist. Zachariah prays to the Lord when the boy was being circumcised:
(NASB)

76 And you, child, also will be called the prophet of the Most High;
For you will go on before the Lord to prepare His ways;
77 To give His people the knowledge of salvation
By the forgiveness of their sins,
78 Because of the tender mercy of our God,
With which the Sunrise from on high will visit us,
79 To shine on those who sit in darkness and the shadow of death,
To guide our feet into the way of peace.”

John is going to prepare the way of the Lord.
Looking to the prophets of Old Testament, it is very clear that the Lord is coming to judge, to punish the wicked. In a way, it seems that the righteous will survive a great calamity.
Zachariah prays that his boy will help the people of the Lord to get the knowledge of salvation by the forgiveness of their sins; so John is going to show light to those sit in darkness; aligning to what we read about Jesus.