The main point of the Book of Jonah is God’s mandate for His people to love other people (considered neighbors), even if they’re unlovable. Jesus subsumes man’s whole moral duty under two categories: Love for God, and love for one’s neighbors. The one who loves God and demonstrates genuine love to his/her neighbor is the person who Jesus states,
“truly I say to you, to the extent that you did it (showed love) to one of these brothers of Mine, even the least of them, you did it to Me.”
In other words, if you love God you will prove it by loving others, even those people who are unlovable.