Luke 18:12. I fast twice in the week.
It is said that these semi-weekly fasts were observed by the Jews because continuous fasting might be injurious. The clays selected were the second and fifth. The reason assigned for the selection of these days is because it was supposed to be on the second day of the week that Moses went up into Mount Sinai to receive the two tables of the law, and it was on the fifth day of the week that he came down on account of the idolatry concerning the golden calf. These days were chosen, not only when public tarts were to be observed, but also when individuals fasted privately.
The only fast commanded in the Mosaic law was in connection with the celebration of the Great Day of Atonement. See note on Leviticus 16:34 (#61). Other fasts were observed, however, in later periods of Jewish history until, in our Lord’s time, the Pharisees carried the practice to an extreme. They fasted often (Matt. 9:14) and disfigured their faces (Matt. 6:16). In the text the Pharisee is represented as regarding this frequent fasting as an evidence of his piety.