Jas 1:7 For that person must not suppose that he will receive anything from the Lord; It only takes faith the size of a mustard seed to move a mountain (Mt 17:20), but without faith our requests fall on deaf ears. If doubt means we won’t receive and faith means we do receive, it only stands to reason that doubt opposes faith. Belief unites us into one body in Christ, but doubt divides us. Division causes instability. James again reinforces this reason prayer goes unanswered by expounding in verse 8, explaining instability through doubt (double-mindedness), or if you prefer he’s explaining doubt through instability.
This post is an excerpt (Question 8.3) from my book Ask James one.