For every action, there is a reaction. For every cause, there is an effect. The children of Israel had agreed to the terms of the covenant with God at the base of Mt. Sinai upon the presentation of the Ten Commandments by Moses. God made a promise to the Israelites and He also made a threat. If His children would simply obey His commandments, He would bless them beyond measure. Disobedience would bring about a two-fold curse from Him. First, they would lose the blessings that God had promised them and second, they would bring down upon themselves His wrath in the form of severe punishments.
God, in His mercy also promised that if after turning from Him, if they confessed their iniquity and repented, He would again heap blessings upon them.
The care and operation of the tabernacle/temple were supported by the offerings of the people. Priests owned no property and thus were dependent upon the people for their sustenance.
A person could consecrate or vow himself, his wife, child or slave to the Lord for His use. Also various animals, houses or fields could be consecrated. God placed a value on each of these items at which they could be bought back or redeemed if the person wished to buy them back. First-born animals could not be consecrated because they already belonged to God.