Biblical references...
Exodus 4:25... "Then Zipporah took a flint and cut off her son’s foreskin and threw it at Moses’ feet, and she said, “You are indeed a bridegroom of blood to me.”
Exodus 18:2... "Jethro, Moses’ father-in-law, took Moses’ wife Zipporah, after he had sent her away"
Numbers 12:1... "Then Miriam and Aaron spoke against Moses because of the Cushite woman whom he had married (for he had married a Cushite woman);"
Deuteronomy 24:1... “When a man takes a wife and marries her, and it happens that she finds no favor in his eyes because he has found some indecency in her, and he writes her a certificate of divorce and puts it in her hand and sends her out from his house"
Psalms 97:10... "Hate evil, you who love the Lord,..."
Proverbs 6:16-19... "There are six things which the Lord hates,  Yes, seven which are an abomination to Him: Haughty eyes, a lying tongue, and hands that shed innocent blood, A heart that devises wicked plans, feet that run rapidly to evil, a false witness who utters lies, and one who spreads strife among brothers."
Malachi 2:16... "For I hate divorce,” says the Lord,..."
Matthew 5:27-28... “You have heard that it was said, ‘You shall not commit adultery’;  but I say to you that everyone who looks at a woman with lust for her has already committed adultery with her in his heart."
Matthew 5:31-32... "It was said, ‘Whoever sends his wife away, let him give her a certificate of divorce’; but I say to you that everyone who divorces his wife, except for the reason of unchastity, makes her commit adultery; and whoever marries a divorced woman commits adultery."
Matthew 17:1-3... Six days later Jesus *took with Him Peter and James and John his brother, and *led them up on a high mountain by themselves.  And He was transfigured before them; and His face shone like the sun, and His garments became as white as light.  And behold, Moses and Elijah appeared to them, talking with Him.
Matthew 18:21-22... Then Peter came and said to Him, “Lord, how often shall my brother sin against me and I forgive him?  Up to seven times?”  Jesus *said to him, “I do not say to you, up to seven times, but up to seventy times seven."
Matthew 19:3-9... Some Pharisees came to Jesus, testing Him and asking, “Is it lawful for a man to divorce his wife for any reason at all?”  And He answered and said, “Have you not read that He who created them from the beginning made them male and female, and said, ‘For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh’?  So they are no longer two, but one flesh.  What therefore God has joined together, let no man separate.”  They *said to Him, “Why then did Moses command to give her a certificate of divorce and SEND her  away?”   He *said to them, “Because of your hardness of heart Moses permitted you to divorce your wives; but from the beginning it has not been this way.  And I say to you, whoever divorces his wife, except for immorality, and marries another woman commits adultery.”
Mark 10:9-12... "What therefore God has joined together, let no man separate.”  In the house the disciples began questioning Him about this again.  And He *said to them, “Whoever divorces his wife and marries another woman commits adultery against her; and if she herself divorces her husband and marries another man, she is committing adultery."
Acts 10:43... "Of Him all the prophets bear witness that through His name everyone who believes in Him receives forgiveness of sins.”
Romans 7:2-3... "For the married woman is bound by law to her husband while he is living; but if her husband dies, she is released from the law concerning the husband.  So then, if while her husband is living she is joined to another man, she shall be called an adulteress; but if her husband dies, she is free from the law, so that she is not an adulteress though she is joined to another man."
1st Corinthians 7:10-15... "But to the married I give instructions, not I, but the Lord, that the wife should not leave her husband (but if she does leave, she must remain unmarried, or else be reconciled to her husband), and that the husband should not divorce his wife.  But to the rest I say, not the Lord, that if any brother has a wife who is an unbeliever, and she consents to live with him, he must not divorce her.  And a woman who has an unbelieving husband, and he consents to live with her, she must not send her husband away.  For the unbelieving husband is sanctified through his wife, and the unbelieving wife is sanctified through her believing husband; for otherwise your children are unclean, but now they are holy.  Yet if the unbelieving one leaves, let him leave; the brother or the sister is not under bondage in such cases, but God has called us to peace."
Hebrews 13:4... "Marriage is to be held in honor among all, and the marriage bed is to be undefiled; for fornicators and adulterers God will judge."

Discussion Thoughts... The first bible mention of "divorce" is the story about Moses Exodus 18:2 and Numbers 12:1 when he "sent away" (divorced) his wife Zipporah and then later married a Cushite woman.  This "divorce" was entirely his doing... apparently he was unhappy with her because of her disgust at having to circumcise her son Exodus 4:25... later Matthew 17:1-3 Moses was seen in heaven so his divorce and remarrying was forgiven.

Numerous scriptures Matthew 5:31-32, Matthew 19:3-9, and Mark 10:9-12 indicate that if you divorce your spouse and then marry someone else you are committing adultery.  These scriptures also suggest that if you spouse commits adultery you are free to divorce your spouse and marry someone else! 

Discussing the Moses situation again... you could draw the conclusion that it was OK for Moses to "divorce" his wife because "he was unhappy with her" --- the counter to that argument is written in Matthew 18:21-22 where Jesus said if someone sins against you, you are to forgive them up to seventy times seven."

In Moses day... Moses decreed that divorce was allowable for almost any reason... see Deuteronomy 24:1.  When Jesus was asked by the Pharisees if divorce was OK Matthew 19:7-8, He explained that Moses allowed it but that it had not always been that way!

I have a problem with calling divorce in itself a "sin"... the acts committed by a spouse such as adultery, murder, not keeping the 10 commandments, the "sins" outlined in Proverbs 6:16-19, etc. are the "sins"... Jesus said he "hates" divorce, but I can find no scripture that says divorce "in itself" is a sin.  If divorce "in itself" is a sin it is forgivable as explained in Acts 10:43.

My Beliefs... My conclusions are simple... I do not believe that divorce "in itself" is a sin... the actions that can accompany a divorce are the "sins" (like adultery and the other "sins" discussed above).

The bible is very clear in Malachi 2:16 that God "hates" divorce, and numerous scriptures Matthew 5:31-32, Matthew 19:3-9, Mark 10:9-12, etc. explain that divorcing your spouse and then marrying someone else creates adultery (adultery is the sin, not the divorce)... these same scriptures explain that if your spouse commits adultery you are free to divorce them and marry someone else. 

I further believe that it is not desirable by God Matthew 19:3-9, Mark 10:9-12, 1st Corinthians 7:10-15 to divorce at all... Moses (Deuteronomy 24:1) decreed that divorce was allowable for almost any reason... Jesus (Matthew 18:21-22) decreed that if someone (your spouse) sins against you, you are to forgive them up to seventy times seven."