A whole chapter of the Bible is devoted to keeping one’s promise. It was Moses who wrote in Numbers 30, “This is the thing which the LORD hath commanded” and continues, “If a man vow a vow… or swear an oath… he shall not break his word, he shall do according to all that proceedeth out of his mouth.” If God is the One who commands promises are to be kept, then breaking a promise or going back on an oath is sin.
The Children of Israel had reached the eastern shore of the Jordan River on their way to the Promised Land, avenging God’s wrath on the Midianites who for centuries had been idol worshippers and refused to worship the One True God. The children of Reuben and the children of Gad, two of Jacob’s sons of the twelve tribes of Israel, “had a very great multitude of cattle: and when they saw the land… behold, the place was a place for cattle,” (Numbers 32:1). The descendants of Reuben and Gad asked of Moses if they could remain east of the Jordan, settling their families and livestock in such a lush valley. Being a part of the Israelite army needed to cross the Jordan and continue in the Children of Israel’s quest to obtain the land promised to Abraham’s descendants, the soldiering men of Reuben and Gad promised, “We ourselves will go ready armed before the children of Israel, until we have brought them unto their place… We will not return unto our houses, until the children of Israel have inherited every man his inheritance.” The men also vowed, “We will not inherit with them on yonder side Jordan, or forward; because our inheritance is fallen to us on this side Jordan eastward,” (vs.17-19).
Moses agreed with the men if they would go armed across the Jordan and lead the army against God’s enemies, they could return and possess the land east of the Jordan River as their inheritance. In his agreement, Moses also gave them this stern warning, “But if you will not do so, behold, ye have sinned against the LORD: and be sure your sin will find you out,” (Numbers 32:23).
Keeping a Promise obeys God;
Not keeping a Promise is sin.