Church Fathers on Luke 20:34

There were two heresies among the Jews, one of the Pharisees, who boasted in the righteousness of their traditions, and hence they were called by the people, “separated;” the other of the Sadducees, whose name signified “righteous,” claiming to themselves that which they were not. When the former went away, the latter came to tempt Him.

The heresy of the Sadducees not only denies the resurrection of the dead, but also believes the soul to die with the body. Watching then to entrap our Savior in His words, they proposed a question just at the time when they observed Him teaching His disciples concerning the resurrection; as it follows, And they asked him, saying, Master, Moses wrote to us, If a brother, &c.

According to the letter of the law, a woman is compelled to marry, however unwilling, in order that a brother may raise up seed to his brother who is dead. The letter therefore kills, but the Spirit is the master of charity.