The Decalogue is the Lord’s statement establishing a contractual relationship between the Lord and his confessor. The primary message of the Decalogue is the First Commandment, with the primary element of the First Commandment being the pronoun “I” and the verb “brought you out”.
It sets the principle of priority and superiority of the Lord’s action to and over the confessor’s actions. The other commandments just explain in more detail the consequences of the Lord’s action described in the First Commandment.
The Decalogue does not have an ethical nature (it is not an imperative for the confessor’s conduct). Rather, it indicates the confessor’s behaviour (attitudes) as a testimony of the Lord’s action (word): the confessor’s conduct is a reaction.
Thus, the confessor’s attitudes bear witness (evidence) of the Lord’s word, they reveal its transforming power. The Decalogue shows the potency of the Lord’s action and the relationship between the Lord and the confessor.