Charles Ellicott Commentary Exodus 23:26

"There shall none cast her young, nor be barren, in thy land: the number of thy days I will fulfil." — Exodus 23:26 (ASV)

There shall nothing cast their young, nor be barren. — Abortions, untimely births, and barrenness, when they exceeded a certain average amount, were always regarded in the ancient world as signs of God’s disfavor, and special expiatory rites were devised for checking them. Conversely, when such misfortunes fell short of the ordinary average, God’s favor was presumed. The promises made here confirm humanity’s instinctive feeling.

The number of thy days I will fulfil. — Compare to Exodus 20:12. Long life is always regarded in Scripture as a blessing. (Psalms 90:10; Job 5:26; Job 42:16–17; 1 Kings 3:11; Isaiah 65:20; Ephesians 6:3, and others.)