“If other emissaries had been sent by God to function as intermediaries between Him and humanity, then Jesus fulfills this role in a pre-eminent way.
As pioneer (Hebrews 2:10) and apostle (3:1), Jesus was sent to bring deliverance and lead His people into the Promised Land (3:7-4:11).
As high priest He makes atonement for sin (2:17-18).
Although the two roles differ, they serve a common goal, namely of enabling the listeners to reach their destination, the city that is to come (13:14).
The listeners are privileged to be addressed as ‘holy brothers and sisters, who share in the heavenly calling’ (3:1).
Let them fix their thoughts on Jesus the faithful Son who is the perfect model, and hold firm to Him as ‘our apostle and high priest’ (3:1).
And they are to avoid, at all costs, the negative example of the Israelites who, by their disobedience to God, fell in the wilderness and failed to reach the promised rest (3:7-19).”
–Peter T. O’Brien, God Has Spoken in His Son: A Biblical Theology of Hebrews, ed. D. A. Carson, vol. 39, New Studies in Biblical Theology (Downers Grove, IL; London: IVP Academic: An Imprint of InterVarsity Press; Apollos, 2016), 64-65.