Matthew Poole and continuators on Matthew 6:5

5 And when thou prayest, thou shalt not be as the hypocrites are, for they love to pray, standing in the synagogues and in the corners of the streets, that they may be seen of men, Verily I say unto you, They have their reward.

Our Saviour here cautioneth them against the same thing in Prayer, as he had done before in giving Alms, viz. Hypocrisie and Ostentation, doing this Duty upon that Design meerly to be taken notice of, and applauded by Men, it was Lawful to pray standing in the Synagogues, but not to do it meerly to be taken notice of by Men, for devout Persons, nor yet to confine themselves to praying in the Synagogues, if they chose to pray standing, that they might be more Conspicuous, and in the Synagogues; because those places were more Holy (as they might Dream) Or, which seems rather to be here meant, because there most People would see them, for which purpose only, they chose Corners of Streets, as was the old Popish Custom, upon which Account they set up Crosses, at three way Leets, &c. these things were sinful, but to pray standing was usual, Mar. 11.25. and to pray in the Synagogues, and in the Temple standing as usual, Luk. 18.13. But those who do it meerly for Vain-Glory, have their reward, and must expect none from God.