The first commandment is the most important of them all, for from it derives the authority for all of the others. The statement, anokhi Adonai eloheykha, "I am the LORD your God" includes the idea that there is only one God, who is Judge and Master of the universe.
Note that the word anokhi ("I") is used instead of the more common word ani, suggesting the uniqueness of God. The word eloheykha ("your God") is in the second person singular, rather than in the plural. Each person (individually) must recognize that the God who created him or her is entirely unique, without rival, and entirely sovereign.
There are no mediators in this encounter -- the soul stands before God alone. We know from Exodus 20:18-21 that the Jews were unable to withstand hearing these commandments and asked Moses to be their mediator. Moses, by God's grace, was given the ability to receive the full content of the Torah at Sinai on behalf of Israel, and later Yeshua Himself became the Mediator of the better covenant than that ratified by the elders of Israel at Sinai.
It is interesting that God used the phrase asher hotzeitikha mei'eretz mitzraim ("who delivered you from the land of Egypt") instead of appealing to Himself as Creator of heaven and earth. Why? The sages comment that this was to instill a sense of gratitude among the Jews, since they were especially chosen to be delivered by God's direct intervention, and this was unique among all the nations of the earth. The phrase mibeit 'avadim ("the house of slaves") alludes to the fact that the Egyptians were descendants of Ham (Gen. 10:6), and the Israelites were actually made slaves in a house of slaves.
The First Commandment is absolutely basic and fundamental to all else that follows. Until we are personally willing to accept Adonai as our God, the rest of the commandments are not likely to be obeyed.
The God of Israel is calling us to obey the glorious truth that He alone is our God. Are we willing to obey?