That's not true. Jesus Christ and St. Stephen (Acts) forgive, and ask the Father's forgiveness on, those who killed them and who did not show the least repentance.
(I posted on imprecatory prayer which I borrow this from:
http://www.freerepublic.com/focus/chat/3164893/replies?c=60).
Jesus prayed for those who would convert and believe on him, not those who would never in their lives believe on him, and would always in their lives reject and hate him. Such people will never see the Kingdom of heaven and are destined for eternal damnation. Which is what they ask for, they reject God, so they will see eternal separation from God.
Shortly before Christ was arrested, he prayed:
John 17
"5 And now, O Father, glorify thou me with thine own self with the glory which I had with thee before the world was.
6 I have manifested thy name unto the men which thou gavest me out of the world: thine they were, and thou gavest them me; and they have kept thy word.
7 Now they have known that all things whatsoever thou hast given me are of thee.
8 For I have given unto them the words which thou gavest me; and they have received them, and have known surely that I came out from thee, and they have believed that thou didst send me.
9 I pray for them:
I pray not for the world, but for them which thou hast given me; for they are thine."
I doesn't mean the person is cleansed of all sin: they can't be cleansed unless they repent. But it does mean the assailant's victim has no desire to obtain revenge, only the sinner's conversion, well-being and redemption.
Yes, the Bible clearly says that vengeance is the Lord's. So we know that we are not to seek vengeance against someone who attacks us. It also says that the civil government does (should) wield the "power of the sword" for a definite purpose of God:
Romans 13
"1 Let every soul be subject unto the higher powers. For there is no power but of God: the powers that be are ordained of God.
2 Whosoever therefore resisteth the power, resisteth the ordinance of God: and they that resist shall receive to themselves damnation.
3 For rulers are not a terror to good works, but to the evil. Wilt thou then not be afraid of the power? do that which is good, and thou shalt have praise of the same:
4 For he is the minister of God to thee for good. But if thou do that which is evil, be afraid; for he beareth not the sword in vain: for he is the minister of God, a revenger to execute wrath upon him that doeth evil."
We know that the Bible teaches that our own physical self-defense is our duty when we are bodily attacked by some random stranger. I found this link to address that topic fairly well:
http://www.biblicalselfdefense.com/.
With the altercation ended, do we then forgive the random attacker, that's the question before us. The random attacker is a heathen, since the act is ungodly. Yes, we could pray for the heathen's conversion, but we ought not to leave out that, if God, in his sovereign election, does not save that person, that God would remove them from tormenting Christians, as he would see fit.
We really ought to always be praying
for our own relief and the relief of all of God's children - God provides relief from wickedness to the faithful who pray for relief; he hears the prayers of his people. He does not hear the prayers of the wicked, and, when he chastises his children who have strayed from him and have bloody hands themselves, he does not hear their prayers until they repent from their sins:
Isaiah 1
"15 And when ye spread forth your hands, I will hide mine eyes from you: yea, when ye make many prayers, I will not hear: your hands are full of blood.
16 Wash you, make you clean; put away the evil of your doings from before mine eyes; cease to do evil;"
Isaiah 1 goes on to teach of God's chastisement of his people whom he loves (note the promise of BOTH reward and punishment, which is included with the admonition):
"17 Learn to do well; seek judgment, relieve the oppressed, judge the fatherless, plead for the widow.
18 Come now, and let us reason together, saith the Lord: though your sins be as scarlet, they shall be as white as snow; though they be red like crimson, they shall be as wool.
19 If ye be willing and obedient, ye shall eat the good of the land:
20 But if ye refuse and rebel, ye shall be devoured with the sword: for the mouth of the Lord hath spoken it."
Of course, scarlet and crimson signify sin, snow and wool, purity.
And what did national Israel do to merit such chastisement ?
Isaiah 1 continues:
"21 How is the faithful city become an harlot! it was full of judgment; righteousness lodged in it; but now murderers.
22 Thy silver is become dross, thy wine mixed with water:
23 Thy princes are rebellious, and companions of thieves: every one loveth gifts, and followeth after rewards: they judge not the fatherless, neither doth the cause of the widow come unto them."
Of course this was referring to national Israel, but it stands as instructive to all nations.
The following verses then point to the coming attacks of foreign armies against ancient Israel, culminating in the effective divorce that would be occur in AD 70 with the destruction of the temple, and then the New Covenant in which the New Testament Church, the true believers in Christ (the converts), would be God's chosen people, the elect; the bride of Christ:
"24 Therefore saith the Lord, the Lord of hosts, the mighty One of Israel, Ah, I will ease me of mine adversaries, and avenge me of mine enemies:
25 And I will turn my hand upon thee, and purely purge away thy dross, and take away all thy tin:
26 And I will restore thy judges as at the first, and thy counsellors as at the beginning: afterward thou shalt be called, The city of righteousness, the faithful city.
27 Zion shall be redeemed with judgment, and her converts with righteousness."