HaShem is a jealous Elohim (Exodus 34:14). Isra’el is His wife and He is a jealous Husband (Isaiah 54:5, Jeremiah 3:20-21). In order to show Isra’el that He expected her to be faithful, He used a familiar cultural practice to demonstrate how He would decide Isra’el’s unfaithfulness and its consequences if she aroused His jealousy.
This blessing was spoken to put the memorial name of God on His people: Ehyeh Asher Ehyeh, yod-hey-vav-hey. Adonai is the ‘name’ used today because the verbally spoken memorial name given to Moshe has been lost.