Verse 38 is quoted in Formula of Concord, Solid Declaration, Article 7: Holy Supper (SD 7.36) to support the argument against transubstantiation. For, "the divine essence is not transformed into the human nature, but that the two unaltered natures are personally united" in Jesus (SD 7.36).
Verse 43 is quoted in Apology of the Augsburg Confession, Article 4: Justification (AP 4.83) as solid proof that "We receive the forgiveness of sins.. through [Jesus'] name, that is, on account of him, and therefore not on account of our merits and not on account of our contrition, attrition, love, acts of worship, or works" (AP 4.83).
Verse 43 is quoted again in Apology of the Augsburg Confession, Article 12: Repentance (AP 12.65) as part of a familiar argument. "Therefore the only way that we receive the forgiveness of sins is through the name of Christ, that is, because of Christ, and not because of any of our merits or works" (AP 12.65).
And in case that wasn't enough, verse 43 is quoted again in Apology of the Augsburg Confession, Article 20: Good Works (AP 20.2) arguing, yep, "that the forgiveness of sins takes place freely on account of Christ, that Christ--and not our works--is the atoning sacrifice for sin" (AP 20.2).
Psalm 118:1-2, 14-24
Verse 18 is quoted in Apology of the Augsburg Confession, Article 12: Repentance (AP 12.49) to show that God "terrifies... in order to make room for consolation and vivification, because hearts that do not feel the wrath of God loathe consolation in their smugness" (AP 12.51).
Verse 4 is quoted in Formula of Concord, Solid Declaration, Article 7: Holy Supper (SD 7.99) within a quote from Luther's Confession concerning Christ's Supper to place the bodily or corporeal Jesus as a reality that will be certainly true again on the Last Day, as it was true after Jesus' resurrection. Jesus can take on a corporeal form when he chooses, but this form or mode is not the same mode as Jesus' spiritual or heavenly modes which yield to neither space nor time.
Don't get too caught up in the questions of Jesus' two natures or good works or how exactly communion is possible. Instead, have a blessed Holy Week, and have fun preaching the risen Jesus. There will be time for deeper conversation once the good news is announced.
Alleluia! Jesus is risen!