Notice verse 7: I will declare the decree: the Lord hath said unto me, Thou art my Son; this day have I begotten thee. 

This is the first time this is mentioned in the Bible. Notice some other places this verse is mentioned:

Acts 13:33 KJV
God hath fulfilled the same unto us their children, in that he hath raised up Jesus again; as it is also written in the second psalm, Thou art my Son, this day have I begotten thee.

Hebrews 1:5 KJV
For unto which of the angels said he at any time, Thou art my Son, this day have I begotten thee? And again, I will be to him a Father, and he shall be to me a Son?

Hebrews 5:5 KJV
So also Christ glorified not himself to be made an high priest; but he that said unto him, Thou art my Son, to day have I begotten thee.

 This is also speaking of the Lord Jesus Christ. If you want to put it like this Jesus is speaking at the moment and saying what His Father spoke unto Him. The word begotten means to birth, to beget. God the Father begat God the Son. Joseph was not the biological father of Jesus. 

Notice the very familiar verse in the Bible; John 3:16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.

It's amazing how other translations put that God had one and only son which is not true. He had only One begotten Son, but He has many sons. 

John 1:11-13 states: He came unto his own, and his own received him not. (12) But as many as received him, to them gave he power to become the sons of God, even to them that believe on his name: (13) Which were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God. 

The One that had the same blood line of His Father died for the strangers so they could have His blood applied to their heart, so they could go to Heaven to be with Him. 

That is salvation in a nutshell! Christ came, born of a virgin, died for the sin of the world, was buried and rose again the third day for me and for you to have life ascended to His Father and is one day coming back for those that are saved. 

The question today is have you been adopted into the family of God? If so, are you telling others how they can be a part of His family? If you are not a part of His family why don't you become a part of His Family today? 

Romans 8:15 KJV
For ye have not received the spirit of bondage again to fear; but ye have received the Spirit of adoption, whereby we cry, Abba, Father.

Psalm 2:1-12 KJV Why do the heathen rage, and the people imagine a vain thing? [2] The kings of the earth set themselves, and the rulers take counsel together, against the Lord, and against his anointed, saying, [3] Let us break their bands asunder, and cast away their cords from us. [4] He that sitteth in the heavens shall laugh: the Lord shall have them in derision. [5] Then shall he speak unto them in his wrath, and vex them in his sore displeasure. [6] Yet have I set my king upon my holy hill of Zion. [7] I will declare the decree: the Lord hath said unto me, Thou art my Son; this day have I begotten thee [8] Ask of me, and I shall give thee the heathen for thine inheritance, and the uttermost parts of the earth for thy possession. [9] Thou shalt break them with a rod of iron; thou shalt dash them in pieces like a potter's vessel. [10] Be wise now therefore, O ye kings: be instructed, ye judges of the earth. [11] Serve the Lord with fear, and rejoice with trembling. [12] Kiss the Son, lest he be angry, and ye perish from the way, when his wrath is kindled but a little. Blessed are all they that put their trust in him.