The Day of Pentecost was the beginning of the New Covenant, God's Covenant of Grace.

In the Old Testament, the day of Pentecost (“Shavuot”) was the beginning of the old Covenant, when the Jewish people accepted God’s law at Mount Sinai.

The Prophet Jeremiah prophesied of God's New Covenant.

"Behold, the days come, saith the LORD, that I will make a new covenant with the house of Israel, and with the house of Judah: not according to the covenant that I made with their fathers in the day that I took them by the hand to bring them out of the land of Egypt; which my covenant they brake, although I was an husband unto them, saith the LORD: but this shall be the covenant that I will make with the house of Israel;

“After those days, saith the LORD, I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people. And they shall teach no more every man his neighbour, and every man his brother, saying, Know the LORD: for they shall all know me, from the least of them unto the greatest of them, saith the LORD: for I will forgive their iniquity, and I will remember their sin no more." - Jeremiah 31:31-34 KJV

In God’s Old Covenant, His law was written on tables of stone. In God’s New Covenant, God's law would be written in the heart of His people. And, in His New Covenant, God would remit the sins of His people.

The new covenant that Jeremiah prophesied of began on the Day of Pentecost with the outpouring of God’s Spirit, God writing His law on the hearts of His followers in the upper room, and Apostle Peter preaching the gospel of the new covenant for the very first time.

"And when the day of Pentecost was fully come, they were all with one accord in one place. And suddenly there came a sound from heaven as of a rushing mighty wind, and it filled all the house where they were sitting. And there appeared unto them cloven tongues like as of fire, and it sat upon each of them. And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance." - Acts 2:1-4 KJV

Peter proceeded to preach the gospel to all the Jews gathered in Jerusalem for the holy day of Pentecost (Shavuot). He preached the gospel of Jesus – that Jesus died for our sins, was buried, and rose again on the third day. Peter then preached how to obey the gospel.

"Now when they heard this, they were pricked in their heart, and said unto Peter and to the rest of the apostles, Men and brethren, what shall we do?

“Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost.

“For the promise is unto you, and to your children, and to all that are afar off, even as many as the Lord our God shall call.

“And with many other words did he testify and exhort, saying, Save yourselves from this untoward generation." - Acts 2:37-40 KJV

To be continued...