David doesn't accept Jonathan’s assurances. On an oath, he says to Jonathan, ‘Thy father certainly knoweth that I have found grace in thine eyes; and he saith, Let not Jonathan know this,’ – the intention to murder David – ‘lest he be grieved.
How necessary it is for us to take steps to keep our faith active and alive. Our faith is constantly under attack, and we must actively prevent it; we must ‘take the shield of faith.’ We do this by deliberate turning our minds to the faithfulness of our God, to the truth of all he has said in his word, and especially his promises to his people. We must remember past deliverances, and past answers to prayer, and know that Christ is ‘the same yesterday, and to day, and for ever.’ Satan knows that our faith is our chief implement of defence and he would like to get us to put it down. But having done so, he pours in all manner of discouragement.