be on somebody's side

be on (one's) side

To be supportive or in aid of one or one's idea, plan, intention, etc. We're all on your side, Jerry. We just want to see this issue resolved as quickly and easily as possible. If that stellar legal team is on her side, then there's a chance she might actually win this case.
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be on somebody’s ˈside

support and agree with somebody: I’m definitely on your side in this.Whose side are you on anyway?
See also: on, side