“Dost thou continue praying even when God continues to deny? An unbelieving heart may have some mettle at hand, but will be sure to jade in a long journey. Faith will throw in the net of prayer again and again, as long as God commands and the promise encourageth. The greyhound hunts by sight, when he cannot see his game he gives over running; but the true hound by scent, he hunts over hedge and ditch though he sees not the hare he pursues all the day long. An unbelieving heart, may be, drawn out, upon some visible probabilities and sensible hopes of a mercy coming, to pray, but when these are out of sight his heart fails him; but faith keeps the scent of the promise and gives not over the chase.”
Paul prayed just three times for his thorn in the fresh to be removed because God had answered that “His grace was sufficient”, but we are to continue to knock (pray) until the answer comes, and may it come mightily in revival.