Keep someone at arm’s length Neutral

Maintain emotional or social distance from someone, avoiding excessive closeness, familiarity or trust. The distance is usually deliberate rather than accidental.

The phrase comes from the concrete reach of a human arm. If another person is held at arm’s length, they remain close enough to see or deal with but not close enough to embrace or come into intimate contact. The physical image naturally developed into a metaphor for cautious social relations. It can describe distrust, a wish for privacy, professional boundaries or a decision not to become emotionally involved. The expression has also been used literally in descriptions of holding objects or people away from the body, so the figurative meaning is easy to visualize. Its history should not be confused with the modern psychological terminology of boundaries, even though that terminology helps explain many present-day uses. The idiom does not necessarily imply open hostility: someone may be polite and cooperative while still keeping another person at arm’s length.

She’s friendly with her coworkers but keeps them at arm’s length.

After the argument, he kept his old friend at arm’s length.

The journalist tried to keep the politician at arm’s length.