Self mutilation is a satanic practice that appears in the Bible when The Prophet of the LORD Samuel confronted the 450 prophets of Baal and 400 prophets of the groves on mount Carmel, when there was the competition about who's God is real and whose is not, for a reminder here are the verses:
1Ki
18:17 ¶ And it came to pass, when Ahab saw Elijah, that Ahab said unto him,
Art thou he that troubleth Israel?
1Ki
18:18 And he answered, I have not troubled Israel;
but thou,
and thy
father's house, in that ye have forsaken
the commandments of
the LORD,
and thou
hast followed Baalim.
1Ki
18:19 Now therefore send,
and
gather to
me all Israel unto mount Carmel,
and the
prophets of
Baal four
hundred and
fifty, and
the prophets
of the groves four hundred, which
eat at Jezebel's table.
1Ki
18:20 So Ahab sent unto all the children of Israel, and gathered the prophets together
unto mount
Carmel.
1Ki
18:21 ¶ And Elijah came unto all the people, and said, How long halt ye between two opinions?
if the LORD
be
God, follow
him: but
if Baal,
then follow him. And the people answered
him not
a word.
1Ki
18:22 Then said Elijah unto the people, I,
even I only, remain a prophet of the LORD; but Baal's prophets
are four hundred and fifty men.
1Ki
18:23 Let them therefore give us two bullocks; and let them choose one bullock for themselves, and
cut it in pieces, and lay
it on wood, and put no fire
under:
and I will dress the other bullock, and lay
it
on wood,
and put
no fire
under:
1Ki
18:24 And call ye on the name of your gods, and I will call on the name of the LORD: and the God that answereth
by fire,
let him
be God.
And all
the people
answered and
said, It
is well
spoken.
1Ki
18:25 And Elijah said unto the prophets of Baal, Choose you one bullock for yourselves,
and dress
it first; for ye
are
many; and
call on
the name
of your
gods, but
put no fire
under.
1Ki
18:26 And they took the bullock which was given them, and they dressed
it, and called on the name of Baal from morning even until noon, saying, O Baal, hear us. But
there was
no voice,
nor any
that answered. And
they leaped
upon the
altar which
was made.
1Ki
18:27 And it came to pass at noon, that Elijah mocked them, and said, Cry aloud: for he
is a god; either he is talking, or he is pursuing, or he is in a journey,
or peradventure he
sleepeth, and must be awaked.
1Ki
18:28 And they cried aloud, and cut themselves after
their manner
with knives
and lancets,
till the
blood gushed
out upon
them.
1Ki
18:29 And it came to pass, when midday was past, and they prophesied
until the
time of the offering of the
evening
sacrifice, that
there
was neither voice,
nor any
to answer,
nor any
that regarded.
1Ki
18:30 And Elijah said unto all the people, Come near unto me. And all the people came near unto him. And he repaired the altar of the LORD
that was broken
down.
1Ki
18:31 And Elijah took twelve stones, according
to the number of the tribes of the sons of Jacob, unto whom the word of the LORD came, saying,
Israel shall
be thy name:
1Ki
18:32 And with the stones he built an altar in the name of the LORD: and he made a trench about the altar, as great as would contain two measures of seed.
1Ki
18:33 And he put the wood in order, and cut the bullock in pieces, and laid
him
on the wood, and said, Fill four barrels with water, and pour
it on the burnt sacrifice, and
on the wood.
1Ki
18:34 And he said, Do
it the second time. And they did
it
the second
time. And
he said,
Do
it
the third
time. And
they did
it the third time.
1Ki
18:35 And the water ran round about the altar; and he filled the trench also with water.
1Ki
18:36 And it came to pass at
the time of the offering of the
evening
sacrifice, that Elijah the prophet came near, and said, LORD God of Abraham, Isaac, and of Israel, let it be known this day that thou
art God in Israel, and
that
I
am
thy servant,
and
that I have done all these things at thy word.
1Ki
18:37 Hear me, O LORD, hear me, that this people may know that thou
art
the LORD
God, and
that thou hast turned their heart back again.
1Ki
18:38 Then the fire of the LORD fell, and consumed the burnt sacrifice,
and the
wood, and
the stones,
and the
dust, and
licked up
the water
that
was in the trench.
1Ki
18:39 And when all the people saw
it, they fell on their faces: and they said, The LORD, he
is the God; the LORD, he
is the God.
1Ki
18:40 And Elijah said unto them, Take the prophets of Baal; let not one of them escape. And they took them: and Elijah brought them down to the brook Kishon, and slew them there.
the self mutilation part appears in verse 28 where they start cutting themselves with knives and lancets to try to wake their non existant god, but it's a futile practice, but you can also see earlier that in verse 26 where these fakes jump up on the altar their "god" was supposed to send fire, they knew there would be no fire, yet in their religious fervor they start slicing themselves.
