God save the king

Solution 1:

For this exact wording, it dates back to at least circa 1367:

Godde saue the kyng
_{Eulogium Historiarum sive Temporis}

For similar phrases, the Oxford English Dictionary has an earlier example from The early South-English legendary; or, Lives of saints (c1300):

‘Sire king,’ he seide, ‘god þe loke and saui þi dignite!’

Translation: "Sire king," he said, "God look over you and save your dignity!"

Solution 2:

From the Wikipedia page on this:

The phrase "God Save the King" is much older than the song, appearing, for instance, several times in the King James Bible... 1st Book of Kings Chapter 1: verses 38–40, ... "And all the people rejoic'd, and said: God save the King! Long live the King! May the King live for ever, Amen"

The King James Bible is an English translation of the Christian Bible for the Church of England, begun in 1604 and completed as well as published in 1611 under the sponsorship of King James I of England.