In the midst of life we are in DEATH

I first heard this in a Clint Eastwood movie-The Outlaw Josie Wales. The character says "Like the good book says in the midst of life we are in debt..."
I can't find it in the Bible.
It also pops up on a Morrisey song.

It's death. It's meant to mean that death is part of life.

"In the midst of life we are in death." Book of Common Prayer, The Burial of the Dead, First Anthem. ("Oxford Dictionary of Quotations," Fifth Edition, edited by Elizabeth Knowles,Oxford University Press, Oxford and New York, 2001).