Expression found in both the OT and the NT. “Son of man” is used in these ways; (1) as a poetic synonym for “man” or “human,” as in Psa 8:4 and 80:17; (2) in Ezekiel as the title by which God regularly addresses the prophet (2:1,3; 3:1, 3); and (3) in Dan. 7 as the identity of the glorious person whom the prophet sees coming with the clouds of heaven to approach the Ancient of Days. “The Son of Man” is a designation of Christ found frequently in the NT. It was Jesus’ favorite designation of Himself to imply both His messianic mission and His full humanity.
IN THE OLD TESTAMENT: “Son of Man” appears often in the OT as a synonym for “man” or “humankind.” In fact, outside Ezekiel and Daniel it is always used in this way (Job 25:6; Isa 56:2; Jer 50:40).
The book of Ezekiel used “Son of Man” more than 90 times to refer to the prophet. His meaning is debated. Some believe the expression simply serves as an editorial convention. Others say it points to his identification with his people or is used to distinguish Ezekiel from other men. In any case, Ezekiel exhibited a profound sense of the holiness and majesty of God, and the phrase is at least intended to mark the distance that separated the prophet, as human, from Yaweh.
The most important occurrence of the title “Son of Man” in the OT is in Dan 7:13. The context is the slaying of the terrifying fourth beast of Dan 7, whereupon “one like the Son of Man” appears before the Ancient of Days and receives everlasting dominion and glory. While some have interpreted this divine being as a symbol for faithful Jews or “saints of the Most High,” it is best to see this as a clear reference to Messiah. Jesus often designated Himself as such and the clouds of heaven appear again in association with the second coming of Christ (Rev 1:7). Here the Lord Jesus is distinct will give to Christ a kingdom that will never be destroyed (Dan 2:44).