On: every psalm and song in the daily prayers uses today’s English. Off: all of them use the older “thee and thou”. Until you choose, the Songs of Zechariah, Mary and Simeon use today’s English, as most churches sing them. The Lord’s Prayer and the prayers for the dying show the form most people learned.
Jerome's Latin translation of the Bible, completed around 405 and the standard text of the Western church for a thousand years. The text Luther knew before he learned Greek and Hebrew.
In Scripture — The canon, translation, and how Lutherans read the Bible.