# to be baptized by him

"for John to baptize them" 

# You offspring of vipers

 Vipers are poisonous snakes that are dangerous and represent evil. Here "offspring of" means "being like." Alternate translation: "You evil poisonous snakes" or "You are evil, like poisonous snakes"

# Who warned you ... coming?

John was rebuking the people because they wanted him to baptize them, but they did not want to stop sinning. Alternate translation: "You cannot flee from God's wrath like this!" or "You cannot escape from God's wrath just by being baptized!"

# from the wrath that is coming

"from the punishment that God is sending" or "from God's wrath on which he is about to act"