“and, once made perfect, he became the source of eternal salvation for all who obey him and was designated by God to be high priest in the order of Melchizedek” (Hebrews 5:9-10)
On the cross Jesus said "it is finished" right before he gave up his spirit. With these words, He was signifying that everything He came to do was accomplished, everything written about Him had been fulfilled and the redemption of the entire world was completed. Since there was nothing left to do He ascended into heaven and sat down at the right hand of the Father taking his rightful place as Lord (Mark 16:19; Acts 2:33; Romans 8:34; Ephesians 1:20; Hebrews 1:3; 10:12).
This is an important truth to understand because Jesus is Lord whether you have personally confessed his Lordship. Not recognizing His position does not change it as fact. Peter stated this very thing at Pentecost, “Therefore let all Israel be assured of this: God has made this Jesus, whom you crucified, both Lord and Christ.” (Acts 2: 32-36).
With one marvelous act of obedience on the cross, Jesus was perfectly equipped through this experience to become our High Priest in service to God. With this completed exercise He became both the author and source of eternal salvation to everyone who puts their saving faith in Him.
Everything we know and experience as humans has a beginning and an end. We are bound by time, distance and energy. We set aside periods of rest and recharging by eating, sleeping and drinking. This maintains our body’s health and energy. In light of this, it is hard to wrap our brains around the fact that, Jesus is the source of eternal salvation. Which means that it originated with him, it flows out of him and He is the supply for its power. Jesus told this very truth to the woman at the well in John 4, "Jesus answered, “Everyone who drinks this water will be thirsty again, but whoever drinks the water I give him will never thirst. Indeed, the water I give him will become in him a spring of water welling up to eternal life” (John 4:13-14). Once you participate in this life that Jesus offers He is able to sustain you and keep you forever because Jesus is the wellspring to eternal life and its supply will never be shut off.
This truth rings more clear when we understand that Jesus has been guaranteed this position because God designated Him to be a high priest in the order of Melchizedek.Hebrews 7 gives much more detail about this. "And what we have said is even more clear if another priest like Melchizedek appears, one who has become a priest not on the basis of a regulation as to his ancestry but on the basis of the power of an indestructible life. For it is declared: “You are a priest forever, in the order of Melchizedek.” (Hebrews 7:15-17). With Jesus' resurrection from the dead, he broke the power of death, meaning he can never die again (Romans 6:9; Acts 2:24; Ephesians 1:20-23). Since He cannot die again, it also means that He will live forever. "Now there have been many of those priests, since death prevented them from continuing in office; but because Jesus lives forever, he has a permanent priesthood. Therefore he is able to save completely those who come to God through him, because he always lives to intercede for them" (Hebrews 7:23-25). This is why it is so wonderful that God designated Jesus to be a priest after this order. "For the law appoints as high priests men who are weak; but the oath, which came after the law, appointed the Son, who has been made perfect forever" (Hebrews 7:28).
As if this wasn't enough, God promised Jesus by an oath that He would never change his mind, as so Jesus became the author and source of the salvation we so dearly cherish and cling to. "And it was not without an oath! Others became priests without any oath, but he became a priest with an oath when God said to him: “The Lord has sworn and will not change his mind: "You are a priest forever.’” Because of this oath, Jesus has become the guarantee of a better covenant" (Hebrews 7:20-22). Understanding Jesus' role as our high priest, knowing that he is the source of eternal salvation guaranteed by oath from God is an amazing truth that will encourage and bless you throughout your entire life.