The Service (ITF Rules of Tennis 2026, Rules 16–19)

Rule 17 – Service Action: The server shall stand behind the baseline, between the centre mark and the sideline. The server shall then release the ball (from the hand that is not holding the racket) and hit it with the racket before the ball hits the ground.

Source: Rule 16, Rule 17, Rule 18, Rule 19, Rule 22

Send this to your friend — argument over.