79. It is better to make no vow than to vow what God does not wish to be paid to Him to Whom the promise was made. In the case of Isaac we have an example, for the Lord appointed a ram to be offered up instead of him. Gen. xxii. 13. Therefore it is not always every promise that is to be fulfilled. Nay, the Lord Himself often alters His determination, as the Scriptures point out. For in the book called Numbers He had declared that He would punish the people with death and destroy them, Num. xiv. 12. but afterwards, when besought by Moses, He was reconciled again to them. And again, He said to Moses and Aaron: “Separate yourselves from among this congregation that I may consume them in a moment.” Num. xvi. 21. And when they separated from the assembly the earth suddenly clave asunder and opened her mouth and swallowed up Dathan and Abiram.