Charles Spurgeon Commentary Mark 12:18-23

"And there come unto him Sadducees, who say that there is no resurrection; and they asked him, saying, Teacher, Moses wrote unto us, If a man`s brother die, and leave a wife behind him, and leave no child, that his brother should take his wife, and raise up seed unto his brother. There were seven brethren: and the first took a wife, and dying left no seed; and the second took her, and died, leaving no seed behind him; and the third likewise: and the seven left no seed. Last of all the woman also died. In the resurrection whose wife shall she be of them? for the seven had her to wife." — Mark 12:18-23 (ASV)

No doubt they thought that they had completely entangled him that time. How could he answer such a difficult question as that?

But, you see, they had based their inquiry upon the erroneous supposition that things are to be in another state as they are here; so Jesus was able at once to answer them as effectively as he had just answered the Pharisees and Herodians.