Matthew 6:5

And when thou prayest— Our Lord is here treating of private prayer; for which reason his rules must not be extended to public devotion. The Jews of old observed stated hours of prayer: the Scripture mentions three of them; first, the third hour, answering to our nine o'clock, when the morning sacrifice was offered: secondly, the sixth hour; answering to our twelve o'clock. At this hour we find Peter praying on the house-top, Acts 10:9.; thirdly, the ninth hour, answering to our three o'clock in the afternoon; at which time the apostles Peter and John are said to have gone up to the temple, Acts 3:1. The three are mentioned together, Psalms 55:17. See also Daniel 6:10; Daniel 6:13. At these hours, therefore, the hypocrites took care to be in some public meeting or other, (for so the original word συναγωγαις may be understood,) perhaps in the market-place, or in some court of justice, or in a corner where two streets met, and where there was a concourse of passengers to behold their devotions; which they performed before all present, with a vanity extremely offensive to the great Being whom they pretended to worship. This was the affectation here blamed in the Jews as most abominable to God.