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.
The Lutheran teaching that Christ's body and blood are truly and substantially present in, with, and under the bread and wine of Holy Communion, not merely symbolized or remembered.
In Sacraments — Baptism, the Lord's Supper, confession, and the language around them.