The reason why God granted Jesus unprecedented authority was not just that he was the promised Jewish Messiah, uniquely authorized agent of God; but more precisely because “he is human.”
This status is reflected in Jesus’ favorite self-title, the Son of Man, itself an expression meaning a “human being.”
This phrase appears over 80 times in only 120 or so Gospel pages (using the NASB)!
I think the reason the NT emphasizes the humanity of the Messiah by using “son of man” is to take us back to the most quoted and alluded to OT verse by the NT writers: Daniel 7.13!
There are around 40 NT verses that echo this verse and the one that follows it is also another NT favorite, Daniel 7:14.
The use of the rather unique phrase “son of man” without “the” in John 5:27 further reinforces the reason God gives the Son authority to judge: because “he is a human.”
When we break down this verse we see how it fits with Dan 7:13-14 like a puzzle.
John 5:27a reads: “And he [God] gave him [son of man] authority…”
And Dan 7:14a: “And authority was given to him [son of man]…”
Then John 5:27b tells us why: “Because he is son of man [i.e., a human being].”
And Dan 7:13 has already identified the subject as the same exalted, glorified human being.
In fact, the humanity of Jesus is so important that later Paul warns “if someone comes and proclaims another Jesus than the one we proclaimed” (2Cor 11:4) or “a gospel contrary to the one we preached to you” (Gal 1:8), they run the risk of putting themselves under a curse!
This warning is nicely captured by the late prominent Finnish scholar Heikki Räisänen:
“The farther one moves from the Jewish-messianic roots of Christology, the more the humanity of Jesus fades.” (The Rise of Christian Beliefs, p 225)