Though an unbeliever sin in praying, yet it is not a sin for him to pray. There is sin in the manner of his praying; but prayer, as to the act and substance of it, is his duty. He sins, not because he prays, that is required of him, but because he prays amiss, not in that manner that is required of him. There are abominations in the prayers of a wicked man, but for him to pray is not an abomination, it is the good and acceptable will of God, that which He commands.