They were asking a hard question hoping to catch Jesus in an embarassing answer. Would he stick to Scripture?
In that particular confrontation, he did, and even quoted some additional verses.
And, we're left with a disconcerting lesson. Matthew modified it some. Paul, in writing to the Corinthians did, too.
We continue to struggle with the need to obey God's will in troubling situations.
And we continue to see instances of modern-day Pharisees trying to embarass other Christians.