Speak to the people of Israel, that they take for me a contribution. From every man whose heart moves him you shall receive the contribution for me.
Exodus 25:2 ESV

It was common practice to exchange gifts for marriage: a bride price given to the bride and her family from the groom and a dowry given to the groom by the bride and her family. A bride price without a dowry could make the bride into a concubine, a wife with the added obligations of servitude.

When God brought Israel out of Egypt, he gave them a bride price from Egypt's coffers--it all belongs to him anyway. Here in Exo 25:2, he asks for part of that bride price back from Israel as a dowry. The exchange establishes the foundation for a healthy relationship instead of one of slavery.

Of course, disobedience to the covenant and commandments brings another kind of obligation and slavery. Only Yeshua can resolve that one.