Be merciful unto me, O God. This petition includes all the good for which we come to throne of grace. If we obtain mercy there, we need no more to make us happy. It implies likewise our best plea, not our merit, but God's mercy, his free, rich mercy. We may flee to, and trust the mercy of God, when surrounded on all sides by difficulties and dangers. His enemies were too hard for him, if God did not help him. He resolves to make God's promises the matter of his praises, and so we have reason to make them. As we must not trust an arm of flesh when engaged for us, so we must not be afraid of an arm of flesh when stretched out against us. The sin of sinners will never be their security. Who knows the power of God's anger; how high it can reach, how forcibly it can strike?