Exodus 35:1
And Moses gathered all the congregation of the children of Israel together, and said unto them, These are the words which the LORD hath commanded, that ye should do them. And Moses gathered all the congregation of the children of Israel together, and said unto them, These are the words which the LORD hath commanded, that ye should do them.
Moses gathered the whole congregation of the children of Israel together in order to communicate to them the words the Lord had commanded for them to do. This gathering came after he had spent forty days and forty nights with God, eating nothing and drinking nothing, listening to God's words. When he came down from the mount, Israel had made a golden calf and was worshiping it.
In that gathering he gave the people opportunity to manifest their position by coming out on the Lord's side, not merely on Moses' side. Those who yielded were preserved alive, while those who did not yield lost their lives, so the gathering was the Lord testing His people. Read with Exodus 31, 35, and 36, it points to the exactness, skill, wisdom, and perfection required in the Lord's service, following the pattern God had shown Moses.