The evidence shows that Jesus became High Priest when he got baptized in 29 C.E. What is the evidence? At his baptism, Jesus presented himself for sacrifice on the altar of God’s “will.” (Gal. 1:4; Heb. 10:5-10) Since that symbolic altar has been in existence from Jesus’ baptism onward, the great spiritual temple​—which represents the arrangement for pure worship of Jehovah based on the ransom—​must also have come into existence at that point. The altar is a key feature of that spiritual temple.​—Matt. 3:16, 17; Heb. 5:4-6.

With the great spiritual temple in place, a high priest was needed to officiate there. To fill that need, Jesus was anointed “with holy spirit and power.” (Acts 10:37, 38; Mark 1:9-11) Yet, how can we be sure that Jesus was appointed as High Priest before his death and resurrection? We find a compelling reason when we consider the example of Aaron and his successors who served as high priests under the Mosaic Law.

As required by the Law, only the high priest could enter the Most Holy of the tabernacle and, later, the temple’s Most Holy. This compartment was separated from the Holy by a curtain. The high priest passed beyond that curtain only on the Day of Atonement. (Heb. 9:1-3, 6, 7) Just as Aaron and his successors were anointed as high priests before entering “through the [literal] curtain” of the tabernacle, Jesus must have been appointed as the High Priest of Jehovah’s great spiritual temple before he died and thereafter passed “through the curtain, that is, his flesh” to heavenly life. (Heb. 10:20) For this reason, the apostle Paul referred to Jesus as coming “as a high priest” and then passing “through the greater and more perfect tent not made with hands” and into “heaven itself.”​—Heb. 9:11, 24.

There is no distinction between when the new covenant was validated and when it was inaugurated. Why not? When Jesus ascended to heaven and offered up his perfect human life in our behalf, he set in motion a process that validated, or legalized, the new covenant. That same process also inaugurated the covenant, or put it into effect. What steps were involved in doing so?

First, Jesus appeared before Jehovah; next, Jesus offered up the value of his sacrifice to Jehovah; and finally, Jehovah accepted the value of Jesus’ shed blood. Until these steps were taken, the new covenant was not operative.

The Bible does not tell us exactly when Jehovah accepted the value of Jesus’ sacrifice. Accordingly, we cannot pinpoint a specific time when the new covenant was validated and also put into effect. Nevertheless, we do know that Jesus ascended to heaven ten days before Pentecost. (Acts 1:3) At some point during that short period of time, he presented the value of his sacrifice to Jehovah, who accepted it. (Heb. 9:12) Proof that the new covenant was now operative was visibly evident at Pentecost. (Acts 2:1-4, 32, 33) The new covenant was then obviously in place and working.

In summary, the new covenant was validated and inaugurated after Jehovah accepted the value of Jesus’ shed blood and brought the anointed into that covenant. The covenant then became operative with the High Priest, Jesus, serving as its Mediator.​—Heb. 7:25; 8:1-3, 6; 9:13-15.