Levitical order of priesthood has limitation in the sense that they were subjected to weakness of the flesh and because death prevented them from continuing in the office (Hebrews 5:1-3, Hebrews 7:23). Jesus was chosen by God to occupy the office. He had a permanent priesthood, therefore he is able to save completely those who come to God through Him because He always live to intercede for mankind.

[26] In the same way, the Spirit helps us in our weakness. We do not know what we ought to pray for, but the Spirit himself intercedes for us through wordless groans. [27] And he who searches our hearts knows the mind of the Spirit, because the Spirit intercedes for God’s people in accordance with the will of God. Romans 8:26-27

Expounding the Book of Hebrews - Chapter 5