take somebody's side
pick somebody's side , also: take the side of somebody
choose somebody's side

And you cannot take my side, not so long as we're in their hands.

I find myself more often than not taking the woman's side.

He took the left side as Big stood at the right.

Robert's going to walk over to take his side of things.

Wouldn't doing nothing to change the policy also be taking sides?

I certainly could never take sides against one of my parents.

A time comes when a man has to take sides.

Even a week before the big game, people are already taking sides.

But I didn't come over here to take sides about anything.

If there is only on in ten who'll take your side then we will go.