From page 84 of ‘The Cost of discipleship’
Jesus does not enjoin his disciples to marry, but he does sanctify marriage according to the law by affirming its indissolubility and by prohibiting the innocent party from remarrying when the guilty partner has broken the marriage by adultery. This prohibition liberates marriage from selfish, evil desire, and consecrates it to the service of love, which is possible only in a life of discipleship. …
It would appear that by affirming the indissolubility of marriage Jesus contradicts the law of the Old Testament. But there is another passage (Matt. 19.8) which shows that in fact he is at one with the law of Moses. There he says that divorce was permitted to the Israelites ‘for your hardness of heart’ – in other words, it was to preserve them from worse excesses.