Leviticus 16:11 And Aaron shall bring the bullock of the sin offering, which is for himself, and shall make an atonement for himself, and for his house, and shall kill the bullock of the sin offering which is for himself:
12 And he shall take a censer full of burning coals of fire from off the altar before the LORD, and his hands full of sweet incense beaten small, and bring it within the vail:
13 And he shall put the incense upon the fire before the LORD, that the cloud of the incense may cover the mercy seat that is upon the testimony, that he die not:
Under the law, the priest was to take coals of fire off the altar with incense and make intersession for himself and for the people. It was an act of his intersesory duty.
This(coals of fire) was also quoted again in Proverbs. Let's look at it.
Prov 25v21 If thine enemy be hungry, give him bread to eat; and if he be thirsty, give him water to drink:
22 For thou shalt heap coals of fire upon his head, and the Lord shall reward thee
When this action was done by the priest under the law, it was put on the mercy seat before the Lord, not as an act of revenge or to do harm, but to bring in mercy and stay death and harm away.
Now, let's go to Romans where it was quoted directly again and let's see the context
Romans 12v17 Recompense to no man evil for evil. Provide things honest in the sight of all men.
18 If it be possible, as much as lieth in you, live peaceably with all men.
19 Dearly beloved, avenge not yourselves, but rather give place unto wrath: for it is written, Vengeance is mine; I will repay, saith the Lord.
20 Therefore if thine enemy hunger, feed him; if he thirst, give him drink: for in so doing thou shalt heap coals of fire on his head.
21 Be not overcome of evil, but overcome evil with good.
The text is talking about forgiveness and not recompensing evil for evil. That is, don't pay people evil for the evil that they do to you.
Talks about striving to live at peace with all men, not avenging yourself but rather leaving vengeance for God. We are to let God repay. But how did God repay us for our sins and evil? He took upon himself the punishment for our sins. Meaning God's vengeance was and is forgiveness and mercy.
Verse 20 now begins with "Therefore", meaning it draws its meaning from the previous text which talks about God's vengeance which is forgiveness and mercy. Paul couldn't have asked that we shouldn't repay evil for evil and then in the same vain ask that we repay evil for evil by heaping coals of fire on the person we just fed to show love for the evil done to us. It doesn't follow.
And just in case you missed what he said in verse 20, which was a figure of speech, he comes again in verse 21 and says
Be not overcome of evil, but overcome evil with good.
To repay evil for evil would be to take vengeance into your own hands and take heaping coals of fire as literal. Rather, Paul explains heaping coals of fire upon your enemy's head as overcoming evil with good. What is the good? Forgiveness and mercy.
We do not bless people so that wrath can come upon them.
the love of God causes us to actively forego the fleshly desire for vengeance.
The Word teaches us to never repay evil with evil.
There is no other way to say this - don’t!
We don't do good to those who hate us in order that they might die or be disgraced.
It is the Lord’s will that we overcome evil with good.
Let's see how Jesus puts this
Matt 5v43 Ye have heard that it hath been said, Thou shalt love thy neighbour, and hate thine enemy.
44 But I say unto you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you;
45 That ye may be the children of your Father which is in heaven: for he maketh his sun to rise on the evil and on the good, and sendeth rain on the just and on the unjust
He says not to repay evil for evil, but rather to bless them that curse you and do good to them who hate you and use you, so that you can be examples of your father which is in heaven because that's what He does, that's who He is. He is kind to the unthankful and the evil.
Quoted again in the book of Luke.
Luke 6v27 But I say unto you which hear, Love your enemies, do good to them which hate you,
28 Bless them that curse you, and pray for them which despitefully use you.
29 And unto him that smiteth thee on the one cheek offer also the other; and him that taketh away thy cloke forbid not to take thy coat also.
30 Give to every man that asketh of thee; and of him that taketh away thy goods ask them not again.
31 And as ye would that men should do to you, do ye also to them likewise.
32 For if ye love them which love you, what thank have ye? for sinners also love those that love them.
33 And if ye do good to them which do good to you, what thank have ye? for sinners also do even the same.
34 And if ye lend to them of whom ye hope to receive, what thank have ye? for sinners also lend to sinners, to receive as much again.
35 But love ye your enemies, and do good, and lend, hoping for nothing again; and your reward shall be great, and ye shall be the children of the Highest: for he is kind unto the unthankful and to the evil.
36 Be ye therefore merciful, as your Father also is merciful
The “coals of fire on his head” as used by Paul is figurative language to mean by feeding our enemy and doing them good we incite their conscience to recognize the love of God in our forgive for their evil done to us.
This so clear that it's so difficult to miss. It'll take some level of great dishonesty for anyone to teach otherwise.
We are to be imitators of God as dear children and to walk in love and not be vindictive
Ephesians 5
1 Be ye therefore followers of God, as dear children;
2 And walk in love, as Christ also hath loved us, and hath given himself for us an offering and a sacrifice to God for a sweetsmelling savour.
I hope this is clear?
You are blessed!