Out of the Abundance of the Heart the Mouth Speaketh as Hearts Are Changed by the Spirit of God

"O generation of vipers, how can ye, being evil, speak good things? for out of the abundance of the heart the mouth speaketh." - Matthew 12:34

"A good man out of the good treasure of his heart bringeth forth that which is good; and an evil man out of the evil treasure of his heart bringeth forth that which is evil: for of the abundance of the heart his mouth speaketh." - Luke 6:45

Jeremiah and Ezekiel prophesied of the New Covenant that God would make with the house of Israel.

"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." - Jeremiah 31:33 (Jeremiah 31:31-34)

"A new heart also will I give you, and a new spirit will I put within you: and I will take away the stony heart out of your flesh, and I will give you an heart of flesh." - Ezekiel 36:26 (Ezekiel 36:25-27)

On the Day of Pentecost, the New Covenant began when God poured out His Spirit, writing His law in the hearts of those disciples gathered in the upper room.

Out of the abundance of their new hearts, their mouths spoke. God changed their hearts, and as a result, their words were changed.

"And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance." - Acts 2:4

Our hearts are changed when we obey the gospel.

"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.

Just like on the Day of Pentecost, when we are filled with the good treasure of His Spirit, out of the abundance of our hearts, our mouths will speak. (2 Corinthians 4:6-7, Acts 19:6, Acts 10:44-48).