Satan would hinder the success of the saints’ prayers by getting them to be such as would be unwelcome with God.

         First way of Hinderance.  Satan endeavours to hinder the welcome of the saints’ prayers with God, that they may be cast as a petition out of court which God will not look on.  He labours to hinder even the entertainment of our prayers in heaven.  Now our prayers may several ways be stopped at heaven’s door, and denied that gracious access which God useth to give.  I speak now of saints’ prayers.  As for the prayers of the wicked, there is one law for them all —to be cast over the bar and the door shut upon them.  The tree must be good before the fruit it bears can be sweet on God’s palate.  Now the stoppage which the saint’s prayer meets withal, springs not from any unwillingness in God to give out his mercy, or any dislike to have beggars at his door.  Adeo pla­cet Deo dare, ut propter hoc omnia creavit, volebat enim habere quæ et quibus dare—God is so delighted with acts of mercy, that therefore he made the world, and all in it, that he might have suitors to beg and alms to give those suitors.  But from ourselves we put the stones into the lock, which hinders the turning of prayer’s key in it, and so indeed we shut the door of mercy upon ourselves.

The devil himself could not immediately hinder a saint’s welcome.  He hath not such command of God's ear, did we not put words into his mouth, and help him to a charge against us. The lies which he, as a false accuser carries to God, shall not prejudice us in God's thoughts or make our prayers less acceptable; but if the accusation be true, God will hear it, though he be a wicked spirit that tells the tale, and we his dear children of whom it is told.  A father, when he hears of some wicked prank his child hath played, will chide and frown on him, though it be an enemy that told him of it.  Now, to instance what miscarriages in a saint hinder their audience at the throne of grace.  1. When the thing prayed for is not according to the will of God.  2. When the end the saint aims at is not levelled right.  3. When with his prayer he joins not a diligent use of the means.  4. When some secret grudge is lodged in his heart against his brother.  5. When there is a want of faith.