Discipline and proclamation. An interesting pair.
A general reference to Psalm 25 is made in Formula of Concord, Solid Declaration, Article 2: Free Will (SD 2.81) . It's actually quite interesting, but I'll let you decide how preachable. We encounter this reference in the list of ideas denied by Lutherans when it comes to free will. In this case, the issue is conversion in this life--does God make the new Christian "a new creature"? The Lutheran answer: No! The old person in us is not destroyed. Indeed, as the psalm reminds us, the life of faith comes from God's forgiving and empowering us. Free will does not necessitate the destruction of the old creature, but the salvation thereof.
Heaven and earth will pass away, but my words will not pass away.
— Luke 21:33
Verse 33 is cited in Formula of Concord, Solid Declaration, Article 7: Holy Supper (SD 7.43) as a reference to the eternal nature of Jesus' promises, particularly around the Lord's Supper.
Be on guard so that your hearts are not weighed down with dissipation and drunkenness and the worries of this life, and that day does not catch you unexpectedly…
— Luke 21:34
Verse 34 is cited in The Augsburg Confession, Article 26: Concerning the Distinction of Foods (AC 26.35), and in Apology of the Augsburg Confession, Article 15: Human Traditions in the Church (AP 15.46). Both of these references are about controlling the body through self-discipline. Significant emphasis is, not surprisingly, made to the distinction between disciplines for the sake of discipleship and disciplines that arise from God's salvation. The Augsburg Confession reference makes a helpful point, that such discipline "should not serve the purpose of earning grace but of keeping the body in a condition that does not prevent performing the duties required by one's calling" (AC 26.38). Self-discipline enables us to effectively serve the needs of the neighbors God gives you.
Be alert at all times, praying that you may have the strength to escape all these things that will take place, and to stand before the Son of Man.
— Luke 21:36
Verse 36 is cited in a footnote of The Large Catechism, The Lord's Prayer, Introduction (LC 3.3.4, n. 164) as an encouragement to prayer.
Two questions come to my mind with these texts and the above references:
What practices do we have that keep us ready to serve our neighbor?
How are we training ourselves to watch for and announce the coming reign of Jesus?
This leads me, then, to a final question: How do these two questions relate to each other?