Isaiah 54:1-10; Psalm 29(30):2,4-6,11-13; Luke 7:24-30
John the baptist is the point at which the great scriptures of the old testament come together in their perfection. The old testament can be seen as a collection of Wisdom books, Prophetic books, and the law. Wisdom literature - John is full of wisdom, knowing how to listen to God, and most of all, knowing who Jesus is. Prophetic - John points to Jesus and shows us the way through repentance to Jesus. And Law - all of the old testament law points to a new final covenant, and that is made concrete in Jesus.
The Old Testament meets the New in their encounters. The pre-birth meeting of Elisabeth and Mary illustrates the wisdom of John, recognising the presence of His and our Lord. The Baptism of Jesus shows how the Old Testament Law is brought to completion in its observance in Jesus. In today's reading Jesus emphasises the need to obey and complete the law, that we should repent of our sins and be baptised. Then the encounters through the disciples of John and Jesus, show us the prophesies being fulfilled, as the blind see, the lame walk (yesterday's Gospel).
Elsewhere, Jesus makes clear that not one dot, not one iota of the Law is dropped - but it is completed through Him.