Why Did Jesus Refer to Himself as the Son of Man?

Though Jesus referred to himself as "God's Son" (John 10:36), he also called himself the "Son of Man". In the Gospel accounts the expression is found nearly 80 times, applying in every case to Jesus Christ, being used by him to refer to himself. (Mt 8:20; 9:6; 10:23) The occurrences outside the Gospel accounts are at Acts 7:56; Hebrews 2:6; and Revelation 1:13; 14:14.

His title “Son of man” reminds us of his being most closely related to man by becoming flesh, being man’s kinsman, and by reason of this, as foreshadowed in the Law, the repurchaser of blood. (Lev. 25:25; Num. 35:19)

The Bible very plainly shows through it's descriptive account of Jesus having ‘become flesh’ (John 1:14), and having ‘come to be out of a woman’ through his conception and birth to the Jewish virgin Mary. (Gal. 4:4; Luke 1:34-36) Because of all of these things, it is fitting for Jesus to have applied the expression "Son of Man" to himself. (John 1:51; 3:14, 15)

This in itself is in no way suggesting that Jesus was only ever merely a man. The Bible says that Jesus was originally in heaven, "but he emptied himself and took a slave’s form and came to be in the likeness of men." (Phil. 2:7)

God sent his Son to the earth by miraculously transferring the life of Jesus from heaven to the womb of a faithful Jewish virgin named Mary. Jesus inherited no imperfections because he did not have a human father. Jehovah God's holy spirit, or active force, came upon Mary, and his power ‘overshadowed’ her, miraculously causing her to become pregnant. (Luke 1:34, 35) Mary then gave birth to a perfect child. (Isaiah 7:14; Matthew 1:22, 23; Mark 6:3)

For more, see:

SON OF MAN - Links to Information (INDEX; Watchtower Online Library)

Son of Man (Insight-2 pp. 1001-1003; Watchtower Online Library)