Hebrews 5:1-10 establishes the basic identity of Jesus as the heavenly high priest, an important and unique contribution Hebrews makes to our understanding of Christ.
Christ was first identified as high priest in 2:17, and 4:14-16, part of last week's lectionary text, presented the basic idea and implications of Jesus being high priest.
But it is not until today's passage that Hebrews begins to really make the case for Jesus being high priest. After a brief digression, the argument is picked up again in chapter 7 and continues from there through chapter 10. Our passage has two sections to it: Verses 1-4 give the definition of and criteria for being a priest and verses 5-10 show how Christ meets these criteria.
The first verse gives the defining function of a high priest, offering sacrifices for sin. While the Jewish high priest played other roles, too, this function is the only one of real concern in Hebrews. Hebrews especially focuses throughout on the high priestly activities on the Day of Atonement (Yom Kippur), the annual ritual where the high priest would atone for the sins of the Jewish people (see Leviticus 16).
Verses 2-3 emphasize a high priest's solidarity with sinners. Verse 2 gives the positive side that a high priest can sympathize with sinners because he himself has experienced weakness. This aspect of Jesus' character was presented in 2:9-18 (especially verses 17-18), revisited in 4:15-16, and will be elaborated later in our passage, verses 7-9. Verse 3 gives the negative side, that because a high priest is himself a sinner he must atone "for his own sins as well as for those of the people" (Leviticus 16:6 covers this requirement). This negative side will provide a key contrast with the sinless Jesus, a point already mentioned in 4:15 and to be elaborated in 7:26-28.
Verse 4 specifies an important prerequisite for anyone to take on the role of high priest: The high priest must be called by God. The original high priest Aaron is the quintessential example, whose calling is recounted in detail in the Old Testament (see Exodus 28:1, 40:12-15; Leviticus 8:1-12; Numbers 18:1-20), and to whom the story of the false claimant Korah and company provides a key counter-example (Numbers 16:1-35).
In actuality, the history of the high priesthood was an inglorious one, the office having become highly politicized, especially in the Maccabean and Roman periods that led into the time of Jesus. Opposition to the corrupt priesthood was one of the factors that led to the formation of the dissident Qumran community, locus of the Dead Sea Scrolls.
Christ's divine appointment to the high priesthood is explained briefly in verses 5-6 (and at much greater length in chapter 7). To twenty-first century readers, the passage's explanation will likely be baffling. The author simply quotes verses from the middle of two different psalms and viola -- we have Jesus as high priest!
The key for the original audience was that both psalms, Psalm 2 and Psalm 110, were widely recognized as messianic prophecies, so it would have been natural for the audience to apply these two verses to Jesus (see Mark 12:35-37 for an important application of Psalm 110; in Hebrews Psalm 110 has been used already in 1:13). The first quote (Psalm 2:7) establishes the Messiah as God's Son; Hebrews already quoted the verse for this very purpose in 1:5. The second quote (Psalm 110:4) is where the priesthood comes in explicitly.
To fully explain how Hebrews applies Psalm 110:4 to Jesus' status as high priest would require a full study of chapter 7, but to summarize briefly: Jesus could not be a regular Jewish priest because, as the Messiah, he is from the tribe of Judah, whereas priests must come from the tribe of Levi. The character of Melchizedek, however, provides an alternative priesthood.
Melchizedek is an obscure figure who appears in the story of Abraham in Genesis 14:17-20. He is said to be both a king and a "priest of God Most High." He appears nowhere else in scripture until his name shows up in this psalm, where the addressee of the psalm -- understood by Jews of this period to be the Messiah -- is said to be a priest in his order. Hence we have the basis for the Messiah to be identified as a high priest, despite the non-Levite ancestry. Particularly important for Hebrews is that he is said in the verse to be a priest "forever," which connects nicely to Christ's immortal post-resurrection status, and which provides a contrast with the mortality of the Levitical priests.
Verses 7-9 move on to address how Jesus met the requirement of the high priest to be able to empathize with those he represents, mentioned in verses 1-2. Jesus' anguish described in verse 7 puts him in solidarity with those he represents by sharing their own experiences of weakness and suffering. The prayers, cries, and tears of verse 7 are usually understood to be a reference to Gethsemane, though it is possible the author is referring to a tradition about Jesus not contained in our Gospels (tears not being mentioned in our Gospel accounts).
That Jesus' cries to be saved from death were "heard" refers to the resurrection -- he was saved, but only after experiencing death first! Language about Jesus learning obedience and being made perfect (verse 9) often surprises readers today, but the author clearly does not see this as compromising Jesus' sinlessness (see 4:15).
Rather, his being "made perfect" refers to the fact that in order for Jesus to be a high priest, he had to share in the experiences of those he represented -- hence he had to suffer. Being perfected means being fitted properly to the role of high priest, and this required suffering. This was described in 2:5-11. The ultimate purpose of Jesus becoming high priest is given at the end of verse 9: "He became the source of eternal salvation for all who obey him." It takes an eternal high priest to bestow eternal salvation!