in a twinkling (or the twinkling of an eye) in an instant; very quickly.
☞ A twinkling is the time taken to wink or blink an eye. The phrase can be traced back to 1 Corinthians 15:52: 'In a moment, in a twinkling of an eye, at the last trump: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed', and it has been in figurative sense since medieval times.