I know, it is hard to figure out this mentality.

If CHRIST were here HE would might quote from Scripture in "for it is written".  HE might quote Genesis 3, Genesis 18, Numbers 30, Psalms 45, Proverbs 31, Ecclesiastes 7 or the many other related Scriptures.  Then HE might say something like "But from the beginning of the creation God made them male and female.  For this cause shall a man leave his father and mother, and cleave to his wife; And they twain shall be one flesh: so then they are no more twain, but one flesh.  What therefore God hath joined together, let not man put asunder.".  

Then HE might say there is nothing holding them back in their service, except their desire and humility to serve.  HE might say "deny yourself, take up your cross and follow me".  HE might say follow the words of my friends, not your friends and teach the children as stated in Titus 2, before expecting blessings.

The power-hungry money changers is a very good example also.