In 29:9-15 we have the objects and the purpose for the enactment of the covenant.
The objects of the covenant were the leaders, the elders, the officers, every man of Israel, the little ones, the wives, and the sojourners with them, from the men who chopped their wood to the men who drew their water (vv. 10-11). The objects also included all those who were there before Jehovah and those who were not there (vv. 14-15).
The purpose of the enactment of the covenant was for the children of Israel to enter into a covenant with Jehovah their God and into His oath, which He was making with them, so that they would keep the words of that covenant and do them that they might prosper in all that they did (vv. 12, 9). This covenant was not an ordinary agreement but a kind of oath. The covenant here may be compared to a contract to which the parties involved sign their names. Such a covenant was made by God though Moses, who was the mediator.
The purpose of the enactment of the covenant was also for God to establish the children of Israel as His people and Himself as their God (v. 13). Both parties, God and the children of Israel, were in agreement and "signed" the covenant. The children of Israel were to do their part, and God was to do His part. This was the enactment of the covenant.