1. Gospel to be engraved in our heart (Ex 13:8-10)
    Deut 6:4-9, 11:18, Jer 31:31-34, Jn 1:12, Acts 5:30-32

God made the people of Israel who had left Egypt always keep the word of God in their hearts. (Ex 13:8-10, Deut 6:4-9, Deut 11:18)

Ex 13:8 And thou shalt shew thy son in that day, saying, This is done because of that which the Lord did unto me when I came forth out of Egypt.
9 And it shall be for a sign unto thee upon thine hand, and for a memorial between thine eyes, that the Lord’s law may be in thy mouth: for with a strong hand hath the Lord brought thee out of Egypt.
10 Thou shalt therefore keep this ordinance in his season from year to year.

Deut 6:4 Hear, O Israel: The Lord our God is one Lord:
5 And thou shalt love the Lord thy God with all thine heart, and with all thy soul, and with all thy might.
6 And these words, which I command thee this day, shall be in thine heart:
7 And thou shalt teach them diligently unto thy children, and shalt talk of them when thou sittest in thine house, and when thou walkest by the way, and when thou liest down, and when thou risest up.
8 And thou shalt bind them for a sign upon thine hand, and they shall be as frontlets between thine eyes.
9 And thou shalt write them upon the posts of thy house, and on thy gates.

Deut 11:18 Therefore shall ye lay up these my words in your heart and in your soul, and bind them for a sign upon your hand, that they may be as frontlets between your eyes.

God promised the Israelis who kept the word of God a new covenant that he would write the word of God in their hearts. (Jeremiah 31:31-34)

Jeremiah 31:31 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:
32 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:
33 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.
34 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.

When we believe in Jesus as the Christ, the Holy Spirit comes upon us. So the word of God is engraved in our hearts. (John 1:12, Acts 5:30-32)

John 1:12 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:

Acts 5:30 e God of our fathers raised up Jesus, whom ye slew and hanged on a tree.
31 Him hath God exalted with his right hand to be a Prince and a Saviour, for to give repentance to Israel, and forgiveness of sins.
32 And we are his witnesses of these things; and so is also the Holy Ghost, whom God hath given to them that obey him.