'Siding' in the Bible

Then Saul became angry with Jonathan and shouted, “You son of a perverse and rebellious woman! Don’t I know that you are siding with Jesse’s son to your own shame and to the disgrace of your mother?

And some of the Gadites, siding with David, went to his strong place in the waste land, great and strong men, trained for war, expert in the use of arms, whose faces were like the faces of lions, and they were quick-footed like roes on the mountains;