Heb 8:10-11, 1 Jn 2:27, 1 Jn 5:20
In the Old Testament, God said that on that day the people of Israel would know God. (Isa 52:6)
Isa 52:6 Therefore my people shall know my name: therefore they shall know in that day that I am he that doth speak: behold, it is I.
The writer of Hebrews said that God will write the word of God in our hearts so that we will all know Him. (Hebrews 8:10)
Hebrews 8:10 For this is the covenant that I will make with the house of Israel after those days, saith the Lord; I will put my laws into their mind, and write them in their hearts: and I will be to them a God, and they shall be to me a people:
The Holy Spirit has been poured out upon us, and we have come to know God. (1 John 2:27, 1 John 5:20)
1 John 2:27 But the anointing which ye have received of him abideth in you, and ye need not that any man teach you: but as the same anointing teacheth you of all things, and is truth, and is no lie, and even as it hath taught you, ye shall abide in him.
1 John 5:20 And we know that the Son of God is come, and hath given us an understanding, that we may know him that is true, and we are in him that is true, even in his Son Jesus Christ. This is the true God, and eternal life.