A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
mat 19:1FINAL DEPARTURE FROM GALILEE--DIVORCE. ( = Mar 10:1-12; Luk 9:51). (Mat 19:1-12)
And it came to pass, that when Jesus had finished these sayings, he departed from Galilee--This marks a very solemn period in our Lord's public ministry. So slightly is it touched here, and in the corresponding passage of Mark (Mar 10:1), that few readers probably note it as the Redeemer's Farewell to Galilee, which however it was. See on the sublime statement of Luke (Luk 9:51), which relates to the same transition stage in the progress of our Lord's work.
and came into the coasts--or, boundaries
of Judea beyond Jordan--that is, to the further, or east side of the Jordan, into Perea, the dominions of Herod Antipas. But though one might conclude from our Evangelist that our Lord went straight from the one region to the other, we know from the other Gospels that a considerable time elapsed between the departure from the one and the arrival at the other, during which many of the most important events in our Lord's public life occurred--probably a large part of what is recorded in Luk 9:51, onward to Mat 18:15, and part of John 7:2-11:54.
mat 19:2And great multitudes followed him; and he healed them there--Mark says further (Mar 10:1), that "as He was wont, He taught them there." What we now have on the subject of divorce is some of that teaching.
Divorce (Mat 19:3-12).
mat 19:3Is it lawful for a man to put away his wife for every cause?--Two rival schools (as we saw on Mat 5:31) were divided on this question--a delicate one, as DE WETTE pertinently remarks, in the dominions of Herod Antipas.
mat 19:4And he answered and said unto them, Have ye not read, that he which made them at the beginning made them male and female--or better, perhaps, "He that made them made them from the beginning a male and a female."
mat 19:5And said, For this cause--to follow out this divine appointment.
shall a man leave father and mother, and shall cleave to his wife: and they twain shall be one flesh?--Jesus here sends them back to the original constitution of man as one pair, a male and a female; to their marriage, as such, by divine appointment; and to the purpose of God, expressed by the sacred historian, that in all time one man and one woman should by marriage become one flesh--so to continue as long as both are in the flesh. This being God's constitution, let not man break it up by causeless divorces.
mat 19:7They say unto him, Why did Moses then command to give a writing of divorcement, and to put her away?
mat 19:8He saith unto them, Moses--as a civil lawgiver.
because of--or "having respect to."
the hardness of your hearts--looking to your low moral state, and your inability to endure the strictness of the original law.
suffered you to put away your wives--tolerated a relaxation of the strictness of the marriage bond--not as approving of it, but to prevent still greater evils.
But from the beginning it was not so--This is repeated, in order to impress upon His audience the temporary and purely civil character of this Mosaic relaxation.
mat 19:9And I say unto you, Whosoever shall put away his wife, except, &c.--See on Mat 5:31.
mat 19:10His disciples say unto him, If the case of the man be so with his wife, it is not good to marry--that is, "In this view of marriage, surely it must prove a snare rather than a blessing, and had better be avoided altogether."
mat 19:11But he said unto them, All men cannot receive this saying, save they to whom it is given--that is, "That the unmarried state is better, is a saying not for everyone, and indeed only for such as it is divinely intended for." But who are these? they would naturally ask; and this our Lord proceeds to tell them in three particulars.
mat 19:12For there are some eunuchs which were so born from their mother's womb--persons constitutionally either incapable of or indisposed to marriage.
and there are some eunuchs which were made eunuchs of men--persons rendered incapable by others.
and there be eunuchs which have made themselves eunuchs for the kingdom of heaven's sake--persons who, to do God's work better, deliberately choose this state. Such was Paul (Co1 7:7).
He that is able to receive it, let him receive it--"He who feels this to be his proper vocation, let him embrace it"; which, of course, is as much as to say--"he only." Thus, all are left free in this matter.