en_tn_condensed/luk/09/62.md

No one ... fit for the kingdom of God

Jesus responds with a proverb to teach the man about being his disciple. Jesus means that a person is not suitable for the kingdom to God if he focuses on people in his past instead of following Jesus. (See: rc://en/ta/man/jit/writing-proverbs and rc://en/ta/man/jit/figs-explicit)

No one who puts his hand to the plow

Here "puts his hand to" something is an idiom that means the person starts to do something. Alternate translation: "No one who starts to plow his field" (See: rc://en/ta/man/jit/figs-idiom and rc://en/ta/man/jit/translate-unknown)

looks back

Anyone who is looking back while plowing cannot guide the plow where it needs to go. That person must focus on looking forward in order to plow well.

fit for the kingdom of God

"useful for the kingdom of God" or "suitable for the kingdom of God"