In the twinkling of an eye
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.
It was later used by Shakespeare in The Merchant Of Venice, 1596:
"I'll take my leave of the Jew in the twinkling of an eye."
See other phrases and sayings from Shakespeare.