Adam Clarke on Acts 23:8

The Sadducees say that there is no resurrection - It is strange, since these denied a future state, that they observed the ordinances of the law; for they also believed the five books of Moses to be a revelation from God: yet they had nothing in view but temporal good; and they understood the promises in the law as referring to these things alone. In order, therefore, to procure them, they watched, fasted, prayed, etc., and all this they did that they might obtain happiness in the present life. See the account of the Pharisees and Sadducees, Mat 3:7; Mat 16:1.