Add to My Library 
The following sections on Matthew 19:11-12 are from The Bible Knowledge Commentary and The Wycliffe Bible Commentary.
From The Wycliffe Bible Commentary:
1) Teaching on Divorce. 19:1-12.
1. Beyond Jordan. From the Greek peran (beyond) came the name “Perea” for the district on the east side of the Jordan River. 3. Is it lawful for a man to put away his wife for every cause? The strict school of Shammai held that divorce was lawful only for a wife’s shameful conduct. Hillel, however, interpreted Deut 24:1 in the widest possible way, and allowed divorce for every conceivable cause. Thus Jesus was being asked, “Do you agree with the most prevalent interpretation (Hillel’s)?” 4-6. Rather than align himself with either position, Jesus cites the purpose of God in creation (Gen 1:27; 2:24).
Since God’s purpose called for man and wife to be one flesh, any disruption of marriage violates God’s will. 7, 8. Why then did Moses command? Their citing Moses (Deut 24:1) and the bill of divorcement in opposition to Jesus showed their misunderstanding of that regulation. For the provision was a protection of wives from men’s caprice, not an authorization for husbands to divorce at will. 9, 10. Except it be for fornication (cf. on 5:31). If fornication be regarded as a general term including adultery (an identification most uncertain in the NT), then our Lord allowed divorce only for the cause of infidelity by the wife. (Among Jews, only husbands could divorce. Mark, in writing for Gentile readers, states the converse also, Mk 10:12). However, if fornication be viewed in its usual meaning, and referred here to unchastity by the bride during betrothal (cf. Joseph’s suspicions, Mt 1:18, 19) then Christ allowed no grounds whatever for divorce of married persons. Thus he agreed neither with Shammai nor Hillel. Such a high and restricted view of marriage would account for the disciples’ remonstrance, It is not good to marry. It seems unlikely that the disciples, after having imbibed the ideals of Jesus, would have felt the limiting of divorce to cases of adultery an intolerable burden. 11. All men cannot receive this saying, i.e., the statement of the disciples. Though at times marriage may not be expedient, not all men are so constituted as to abstain. 12. Some are incapable of marriage because of congenital defects; others because of injury or restrictions imposed by men. Still others may forego the privilege of marriage in order to devote themselves more completely to the service of God (e.g., Paul, 1 Cor 7:7, 8, 26, 32-35).
This statement certainly casts no reflection upon marriage; rather it concludes a discussion in which marriage was exalted to its original pure state. [Everett F. Harrison, The Wycliffe Bible Commentary, New Testament, (Chicago: Moody Press) 1962.]
From The Bible Knowledge Commentary:
19:1-12. Jesus … left Galilee for the last time and headed for Jerusalem through the region of Judea to the east side of the Jordan River. That area was known as Perea. There, as often before, He was followed by large crowds of needy people, and He healed them. But some Pharisees sought to test Jesus through a question: Is it lawful for a man to divorce his wife for any and every reason? The nation was divided over this issue. Followers of Hillel felt a man could divorce his wife for almost any reason, but others, following Shammai, thought one could not divorce his wife unless she were guilty of sexual offense. Without getting involved in the Hillel-Shammai controversy Jesus reminded the religious leaders of God’s original purpose in establishing the marriage bond. God made people male and female (v. 4; Gen. 1:27). In marriage He joins them together in an inseparable bond. This bond is a higher calling than the parent-child relationship, for a man is to leave his father and mother and be joined to his wife in a one-flesh relationship (Gen. 2:24). Therefore what God has joined together, men ought not separate (cho„rizeto„; in 1 Cor. 7:10 this word means “to divorce”). The Pharisees, realizing that Jesus was speaking of the permanence of the marital relationship, asked why Moses made a provision for divorce for people in his time (Matt. 19:7). The Lord’s answer was that Moses granted this permission because people’s hearts were hard (cf. Deut. 24:1-4). “Because your hearts were hard” is literally, “toward your hardness of heart” (skle„rokardian; from skle„ros, “hardness,” comes the Eng. “sclerosis,” and from kardian comes the Eng. “cardiac”). But that was not God’s intention for marriage. God intended husbands and wives to live together permanently. Divorce was wrong except for marital unfaithfulness (cf. Matt. 5:32).
Bible scholars differ over the meaning of this “exception clause,” found only in Matthew’s Gospel. The word for “marital unfaithfulness” is porneia. (1) Some feel Jesus used this as a synonym for adultery (moicheia). Therefore adultery by either partner in a marriage is the only sufficient grounds for a marriage to end in divorce. Among those holding this view, some believe remarriage is possible but others believe remarriage should never occur. (2) Others define porneia as a sexual offense that could occur only in the betrothal period when a Jewish man and woman were considered married but had not yet consummated their coming marriage with sexual intercourse. If in this period the woman was found pregnant (as was Mary; 1:18-19), a divorce could occur in order to break the contract. (3) Still others believe the term porneia referred to illegitimate marriages within prohibited degrees of kinship, as in Leviticus 18:6-18. If a man discovered that his wife was a near relative, he would actually be involved in an incestuous marriage. Then this would be a justifiable grounds for divorce. Some say this meaning of porneia is found in Acts 15:20, 29 (cf. 1 Cor. 5:1). (4) Another view is that porneia refers to a relentless, persistent, unrepentant lifestyle of sexual unfaithfulness (different from a one-time act of illicit relations). (In the NT porneia is broader than moicheia). Such a continued practice would thus be the basis for divorce, since such unfaithful and unrelenting conduct would have broken the marriage bond. (On the subject of divorce and remarriage, see comments on 1 Cor. 7:10-16.)
Whatever view one takes on the exception clause, Jesus obviously affirmed the permanence of marriage. Those who heard His words understood Him in this way, for they reasoned that if there were no grounds for divorce one would be better off never to marry. But this was not what Jesus intended, for God has given marriage to people for their betterment (Gen. 2:18). Marriage should be a deterrent to lustful sin and to unfaithfulness (1 Cor. 7:2). But a few either do not have normal sexual desires (they were born eunuchs or were castrated), or are able to control those desires for the furtherance of God’s program on the earth (Matt. 19:12; cf. 1 Cor. 7:7-8, 26). But not all are able to accept the single role (Matt. 19:11). Many marry and carry out God’s purposes, extending His work in the world.2