Because he is himself weak is perhaps a little heavy after the similar expression in verse 2, but it is clearer than Revised Standard Version‘s “Because of this.” In the Greek, “this” certainly refers to “weakness.” The rendering of weak in the clause because he is himself weak should be expressed in the same way that weak is translated in verse 2.

He must means “it is his duty as high priest.” Barclay has “he is under obligation.” The background of this verse is Leviticus 16.11-14, the high priest’s sacrifice for himself, and 16.15-19, his sacrifice for the people; see also Leviticus 9.7; 16.6, and the comments on Hebrews 2.17. He must may be expressed as “it is necessary for him” or “it is required that he.”

Offer is literally “bring toward” or “present.” This verb is often used of presenting gifts and sacrifices to God. There is no suggestion that the sacrifice might not be accepted, though of course the Old Testament contains examples of sacrifices which were in fact refused.

In a number of languages there is no such neat contrast as not only … but also. However, the same ideas may be expressed as “he must do this … he must also do that.” The last part of verse 3 may be rendered as “he must offer sacrifices to take away the sins of the people, and he must also offer sacrifices to take away his own sins.”

In a number of languages a careful distinction is made between “sins” in the sense of the actual event of doing something wrong, and “sins” as guilt which results from such wrongdoing. It is the latter sense which is focal in this context.

Quoted with permission from Ellingworth, Paul and Nida, Eugene A. A Handbook on The Letter of the Hebrews. (UBS Handbook Series). New York: UBS, 1983. For this and other handbooks for translators see here .