which was made of the seed of David according to the flesh;
There was a promise made to King David in 2 Samuel Chapter 7

And when thy days be fulfilled, and thou shalt sleep with thy fathers, I will set up thy seed after thee, which shall proceed out of thy bowels, and I will establish his kingdom. He shall build an house for my name, and I will stablish the throne of his kingdom for ever

This is the same seed that was promised to Eve in Genesis Chapter 3

And I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heel.

This is the same seed that was promised to Abraham.

That in blessing I will bless thee, and in multiplying I will multiply thy seed as the stars of the heaven, and as the sand which is upon the sea shore; and thy seed shall possess the gate of his enemies;

And certainly the same seed promised to David.

12 And when thy days be fulfilled, and thou shalt sleep with thy fathers, I will set up thy seed after thee, which shall proceed out of thy bowels, and I will establish his kingdom.
13 He shall build an house for my name, and I will stablish the throne of his kingdom for ever.
14 I will be his father, and he shall be my son. If he commit iniquity, I will chasten him with the rod of men, and with the stripes of the children of men:

Concerning his Son Jesus Christ our Lord

Concering whose Son? God's Son. Jesus Christ the Son of God. But Jesus is not just the Son of God. He is also the express image of the Father. The Holy Ghost has been sent in his name. Father, Son and Holy Ghost, these three are one. Hear Oh Israel the Lord our God is one Lord. One God and one Son. Jesus said "I and my Father are one." Jesus Christ is God manifest in the flesh.

And without controversy great is the mystery of godliness: God was manifest in the flesh, justified in the Spirit, seen of angels, preached unto the Gentiles, believed on in the world, received up into glory.

The devils believe in one God!

Thou believest that there is one God; thou doest well: the devils also believe, and tremble.

Philip asked Jesus to show them the Father.

Jesus saith unto him, Have I been so long time with you, and yet hast thou not known me, Philip? he that hath seen me hath seen the Father; and how sayest thou then, Show us the Father?

Isaiah knew this when he said

For unto us a child is born, unto us a son is given: and the government shall be upon his shoulder: and his name shall be called Wonderful, Counsellor, The mighty God, The everlasting Father, The Prince of Peace.

Many Christians have a hard time believing that Jesus is the Father also, but He is. Jesus is everything that the Father is and everything that the Father is, is in Jesus. This is why Jesus could say, "before Abraham was, I AM" He was born in the manger, but he exsisted with God and as God before his birthday.

In the beginning was the Word, and the Word was with God, and the Word was God.

Yes... Jesus Christ was hundred percent man, but the most wonderful thing, is that he was also one hundred percent God at the same time.