This post is all about marking as well as cutting in the Bible. Marking the skin, whether through cutting, branding or tattooing, is mentioned around the ancient world and in the Bible. Whether it is acceptable for the people of God, and if so in what way, is what I aim to discuss. I am mostly here writing against those who argue that God accepts self harm, that it is good to him, that we are told in the Bible to hurt ourselves to please God. I do not believe this. For another rebuttal of this sort of argument, please check out this Lysamena Self Injury Project page.
Marking yourself, or being marked, was quite common in the ancient near eastern world and is mentioned in the Bible. We know that, in ancient Syria, worshippers marked their flesh with signs branded on the wrist or the neck in dedication to their gods Hadad and Atargatis.  We also know, from the inter-testamental book of Maccabees that the followers of Dionysus had the emblem of an ivy leaf branded on them. (3 Maccabees 2:29). Stories of people branded or scarred from loyalty to their gods are found in many cultures including Egyptian, Samaritan, Thracian, Ethiopian and Briton. The marks served to distinguish people by which deity (or tribe) they belonged to.
Identifying marks are also mentioned in the Bible. If a slave wanted to stay with his master forever he was to pierce his ear in the sight of God (Exodus 21:6; Deuteronomy 15:16ff). Cain, the brother of Abel, was marked by God as a sign of protection (Genesis 4:15) – which many state was almost certainly a tattoo.  He was marked, not as a murderer, but as one who would be protected from the wrath of others.
Sometimes the marks denoted that the person was sacred – as in Isaiah 44:5 (“Some will say, ‘I belong to the Lord’; others will call themselves by the name of Jacob; still others will write on their hand, ‘The Lord’s,’ and will take the name Israel.”) Even God himself is marked – he states that Jerusalem is engraved on the palms of his hands (Isaiah 49:16). Marking on the hands is important – in Exodus 13:9 and 13:16 the feasts of the Passover and Redemption of the Firstborn are both said to be remembered as though they were a mark in the flesh. In the vision of Ezekiel in Ezekiel 9:3 it is said that the Taw which the angel is to mark on the foreheads of those faithful is a cross. 
However, the Old Testament also condemns marking – at least marking by oneself. In Leviticus 19:28 we read “Do not cut your bodies for the dead or put tattoo marks on yourselves. I am the Lord.” Cutting for the dead was practised in Israel, despite being forbidden both above and in Deuteronomy 14:1, as can be seen in Jeremiah 16:6 and 41:5 (“eighty men who had shaved off their beards, torn their clothes and cut themselves came from Shechem, Shiloh and Samaria, bringing grain offerings and incense with them to the house of the Lord”). This was connected to the neighbouring Canaanites’ worship of Baal, as demonstrated by the priests of Baal slashing themselves trying to rouse their god in competition with the prophet Elijah (1 Kings 18:28). This may be the reason why Israelites were forbidden to tattoo themselves. Cutting “for the dead” may be indicative of a cult of the dead, to do with worship of a deity or ancestor, or may simply be a mourning rite practised by pagan nations and therefore forbidden to Israel as a nation set apart by God.
While marking the flesh is not forbidden in the Old Testament, it certainly is when done as part of a dedication to a foreign god. The OT does describe acceptable markings, whether branding, tattooing or cuttings, but only when given by God, and not done by oneself. Then a mark can signify that one is a person dedicated to God, protected by him, in the same way as a mark was left on the doorways of those spared during the Passover.
In the inter-testamental period there were discussions about whether it was acceptable for an Israelite to tattoo, brand or otherwise mark themselves, although the majority seem to have connected these with idolatry. The Rabbis of this time contrasted circumcision with pagan tattooing, arguing that the only mark a Jew should carry was that of circumcision. Some pre-Cabbalistic works suggest that God himself had marks on his forehead of certain letters, but this does not seem to have been a majority view.
In the New Testament Paul is the only writer to talk about marks, as he does in Galatians 6:17 (“From now on, let no one cause me trouble, for I bear on my body the marks of Jesus.”) Paul seems to be saying that he has protective marks which show him to belong to Christ, what these marks are he does not state, but they are likely to have been the scars and wounds he had acquired in the service of the Lord. It has been suggested that Paul contrasted his stigma (marks) of Jesus with the stigma of circumcision. Some people have suggested that Paul had the name of Jesus tattooed on himself, but it is unlikely given Paul’s Pharisaic upbringing.
In the book of Revelation there are two marks given – one to the worshippers of the Beast and one for the faithful servants of God. The mark of the Beast is given by man (Revelation 13:16ff) whereas the mark of God is given by the Lord (Revelation 3:12)
The New Testament only once refers to self-cutting – in Mark 5:1-20, which I have talked about elsewhere. To summarise: I do not believe we can infer about self injury and demons from one example, especially given that in the Old Testament there are self-cutters who were not demon-possessed. Indeed some of the self-cutters in the Old Testament were believers, who had nevertheless picked up pagan practises.
I have hoped, here, to try to explain why marking the body, whether by cutting or tattooing, has been seen as wrong. I can, of course, say that with tattooing, there were Christians tattooing themselves with the name of God before people ever made the sign of the cross, so it has an ancient provenance. Our forefathers obviously thought that the prohibition against tattooing was specific in that it talked about paganism, and the worship or dedication to pagan gods. I myself have tattoos, and I do not feel that they are in any way marking me for a false god.
Back to self injury. The Bible is quite clear that – contrary to what some self injurers I have known have said – self harm is not making yourself better, not making you more acceptable to God. I do not believe that those who mortify the flesh are really doing what God wishes. It is one thing to deny yourself, and another to damage the body God has given. That is not to say that I think God will damn anyone for it – I self injure myself – but that it is not what he wants us to do. In the end, God loves us, and he is a God of forgiveness. He can forgive, and heal, self injury – and I think most of us, who self harm and do not want to, are not as sinful as another who perhaps envies, and does not wish to change. The message I have about self harm is that we can stop, with the help of God, maybe not today but some day. At the last we will all be free, and our bodies changed, and the old sorrows will be no more.
 Pseudo-Lucianus, De Syria Dea, 59
 “Stigma” in Theological dictionary of the New Testament. 1964- (G. Kittel, G. W. Bromiley & G. Friedrich, Ed.) (electronic ed.). Grand Rapids, MI: Eerdmans