The reading says the Pharisees tested Jesus by asking Him, “Is it lawful for a man to divorce His wife for just any reason?”
Jesus refers to the original creation to show that divorce was not a part of God’s plan. ‘What God has joined together let not man separate”. Moses allowed it “because of the hardness of their hearts” but Jesus says except for cases of “sexual immorality” it is wrong.
Modern attitudes toward marriage are quite different from the teaching Jesus gives here. For example, a popular alternative to the traditional vow “as long as we both shall live” is “as long as we both shall love”! In light of how Jesus responds to the Pharisee’s questions, how do you think God feels about an attitude like this?