This is one of the key verses of Scripture for several reasons. In the first place, in the midst of a pantheistic and polytheistic society governed by the kings and rulers for whom Paul had just exhorted believers to pray, it was important to reemphasize that there was only one Creator God--the One to whom even kings must give account and the only One to whom we can rightfully pray.
Secondly, Christ Jesus, who was Himself "God . . . manifest in the flesh" and then "received up into glory" (I Timothy 3:16), was nevertheless still "the man Christ Jesus." He is still a man, even though His human body has been resurrected and glorified. Therefore He can, indeed, "be touched with the feeling of our infirmities;" and we can "come boldly" to His "throne of grace, that we may obtain mercy, and find grace to help in time of need" (Hebrews 4:15-16).
Then, because He is both omnipotent God and perfect Man, "in all points tempted like as we are, yet without sin" (v.15). He is uniquely able to serve as the one and only "mediator between God and man." Furthermore, as the only God-Man, fully and eternally both God and man, He is the only one through whom we can reach God's throne in prayer. "I am the way, the truth, and the life," He said, "no man cometh unto the Father, but by me" (John 14:6).
No one else--man or woman, saint or priest, angel or demon--has direct access to God, for the Son is the one mediator between God and man. We can come to God however for "We have an advocate with the Father, Jesus Christ the righteous" (I John 2:1). "Wherefore He is able also to save them to the uttermost that come unto God by Him, seeing He ever liveth to make intercession for them" (Hebrews 7:25). HMM