MIDRASH TEHILLIM
1.....(2.9)
Let me tell of the decree...“You are My son..."
The children of Israel are declared to be sons in the decree of the Torah, in the decree of the Prophets, and the decree of the Writings.
In Torah - "My firstborn son is Israel" (Exodus 4:22).
In Prophets - "Behold My servant shall prosper; he shall be exalted and lifted up, and he shall be very high" (Yeshayahu - Isaiah 52:13), and its also written - "Behold My servant, I will support him, My chosen one, in whom My soul delights" (Yeshayahu - Isaiah 42:1)
In Writings - "I saw in the visions of the night, and behold with the clouds of the heaven, one like a man was coming, and he came up to the Ancient of Days and was brought before Him. And He gave him dominion and glory and a kingdom, and all peoples, nations, and tongues shall serve him..." (Daniel 7:13-14).
2.
Another word on You are My son
God does not say I have a son, but You are a son to Me, as when a master wishing to give pleasure in his slave, says to him, You are as dear to me as a son.