This is an idiom that means "God will bless them with eternal life" or "God will cause them to live forever." (See: [[rc://en/ta/man/translate/figs-idiom]])
# But many who are first will be last, and the last will be first
Jesus is comparing this age to the next age. Those who are important now, God will consider them unimportant when he establishes his rule on earth. Those who seem unimportant now, God will consider them important when he establishes his rule.