Rules

14. The "Let" in Service

The Service is a let:
a. If the ball served touches the net, strap or band, and is otherwise good, or, after touching the net, strap or band, touches the Receiver or anything which he wears or carries before hitting the ground.

b. If a service or a fault is delivered when the Receiver is not ready (see Rule 12).
In case of a let, that particular service shall not count, and the Server shall serve again, but a service let does not annul a previous fault.