Validation of the Law covenant. The apostle Paul says: “Now there is no mediator where only one person is concerned, but God is only one.” (Ga 3:20) In the Law covenant God was one party; the nation of Israel was the other ‘party.’ Because of their sinful condition, the Israelites were unable to approach God in a covenant. They needed a mediator. Their weakness was demonstrated in their request to Moses: “You speak with us, and let us listen; but let not God speak with us for fear we may die.” (Ex 20:19; Heb 12:18-20) Accordingly, Jehovah mercifully constituted Moses mediator of the Law covenant and arranged for animals to be sacrificed to validate the covenant. Moses, of course, was also imperfect and sinful; however, he enjoyed a favorable standing with God, even as Abraham had earlier. (Heb 11:23-28; see DECLARE RIGHTEOUS [How “counted” righteous].) On the occasion of the inauguration of the covenant, Moses officiated, directing the sacrifice of the animals. Then he sprinkled their blood on the scroll or “the book of the covenant.” He read the book to the people, setting forth the terms, and the people responded by agreeing to obey. Moses then sprinkled them (doubtless the representative older men) with the blood, saying: “Here is the blood of the covenant that Jehovah has concluded with you as respects all these words.”​—Ex 24:3-8; Heb 9:18-22.

Inauguration of the New Covenant. After Jesus died and was resurrected, he entered into heaven to appear before the person of God to present his offering, the benefits of which go first to those taken into the new covenant. (Heb 9:24) Here he acted both as High Priest and Mediator. In harmony with the pattern followed at the inauguration of the Law covenant, Jesus Christ presented the value of his sacrifice before God in heaven (even as Moses sprinkled the blood on the book of the Law [for God was not personally present there]). Then, on Pentecost day, 33 C.E., Jesus poured out the holy spirit from God on the first ones brought into the new covenant, about 120 persons. Later that day about 3,000, Jews and proselytes, were added to the congregation. (Ac 1:15; 2:1-47; Heb 9:19) And just as Moses read the Law to the people, so Jesus Christ clearly enunciates the terms of the new covenant and its laws to those sharing in it.​—Ex 24:3-8; Heb 1:1, 2; Joh 13:34; 15:14; 1Jo 5:1-3.