Adam Clarke on Matthew 19:4

He which made them at the beginning - When Adam and Eve were the first of human kind.

Made them male and female - Merely through the design of matrimonial union, that the earth might be thus peopled. To answer a case of conscience, a man should act as Christ does here; pay no regard to that which the corruption of manners has introduced into Divine ordinances, but go back to the original will, purpose, and institution of God. Christ will never accommodate his morality to the times, nor to the inclinations of men. What was done at the beginning is what God judged most worthy of his glory, most profitable for man, and most suitable to nature.