keep somebody at arm's length

keep (one) at arm's length

To keep one a certain distance away, either physical or figurative, in order to afford a level of safety or security or to prevent intimacy. John always keeps his friends at arm's length, so that no one gets close enough to hurt his feelings. My daughter likes to watch me cook, but I make sure to keep her at arm's length so she doesn't get close to anything hot.
See also: keep, length

keep somebody at arm’s ˈlength

avoid becoming too friendly with somebody: He’s the kind of man who’s best kept at arm’s length.
See also: keep, length, somebody