There shall nothing cast their young, nor be barren, in thy land: the number of thy days I will fulfil.

Wesley's Notes

23:26 The number of thy days I will fulfill - And they shall not be cut off in the midst by untimely deaths. Thus hath godliness the promise of the life that now is.

Matthew Henry's Concise Commentary

23:20-33 It is here promised that they should be guided and kept in their way through the wilderness to the land of promise, Behold, I send an angel before thee, mine angel. The precept joined with this promise is, that they be obedient to this angel whom God would send before them. Christ is the Angel of Jehovah; this is plainly taught by St. Paul, 1Co 10:9. They should have a comfortable settlement in the land of Canaan. How reasonable are the conditions of this promise; that they should serve the only true God; not the gods of the nations, which are no gods at all. How rich are the particulars of this promise! The comfort of their food, the continuance of their health, the increase of their wealth, the prolonging their lives to old age. Thus hath godliness the promise of the life that now is. It is promised that they should subdue their enemies. Hosts of hornets made way for the hosts of Israel; such mean creatures can God use for chastising his people's enemies. In real kindness to the church, its enemies are subdued by little and little; thus we are kept on our guard, and in continual dependence on God. Corruptions are driven out of the hearts of God's people, not all at once, but by little and little. The precept with this promise is, that they should not make friendship with idolaters. Those that would keep from bad courses, must keep from bad company. It is dangerous to live in a bad neighbourhood; others' sins will be our snares. Our greatest danger is from those who would make us sin against God.