Jeremiah 31:31 "Behold, the days are coming," says the LORD, "when I will make a new covenant with the house of Israel and with the house of Judah--
Jeremiah 31:33 "But this is the covenant that I will make with the house of Israel: After those days, says the LORD, I will put My law in their minds, and write it on their hearts; and I will be their God, and they shall be My people.
Ezekiel 36:27 "I will put My Spirit within you and cause you to walk in My statutes, and you will keep My judgments and do them.
This was all started in Acts.
Act 1:8 "But you shall receive power when the Holy Spirit has come upon you; and you shall be witnesses to Me in Jerusalem, and in all Judea and Samaria, and to the end of the earth."
Act 2:4 And they were all filled with the Holy Spirit and began to speak with other tongues, as the Spirit gave them utterance.