In an instant.
This is recorded by Robert Manning of Brunne, in Handlyng synne, 1303: “Yn twynkelyng of an ye”

It is also used in the Bible, 1 Corinthians 15:52 (King James Version):

In a moment, in the 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.