What God has joined together let no man put asunder

Meaning

The part of the Christian marriage ceremony that states God's authority over man.

Origin

The injuction is taken from the Bible, Matthew 19:6. It appears first in print in English in Miles Covedale's Bible, 1535:

 Now are they not twayne then, but one flesh. Let not man therfore put a sunder, yt which God hath coupled together.

It is interesting to note that 'asunder' was, in the 16th century, 'a sunder'. The two words have merged into one, in the same way that many nautical terms, like 'aboard', 'amidships' etc. have done.