Many sorrows shall be to the wicked - The meaning here is, probably, that those who will not submit themselves to God in the manner which the psalmist recommends; who are like the horse and the mule, needing to be restrained, and who are to be restrained only by force, will experience bitter sorrows. The psalmist may refer here, in part, to sorrows such as he says he himself experienced when he attempted to suppress the convictions of guilt Psalms 32:3-4; and partly to the punishment that will come upon the impenitent sinner for his sins. The sorrows referred to are probably both internal and external; those arising from remorse, and those which will be brought upon the guilty as a direct punishment.
But he that trusteth in the Lord - He that has faith in God; he that so confides in him that he goes to him with the language of sincere confession.
Mercy shall compass him about - Shall surround him; shall attend him; shall be on every side of him. It shall not be only in one respect, but in all respects. He shall be “surrounded” with mercy - as one is surrounded by the air, or by the sunlight. He shall find mercy and favor everywhere, at home, abroad; by day, by night; in society, in solitude; in sickness, in health; in life, in death; in time, in eternity. He shall walk amidst mercies; he shall die amidst mercies; he shall live in a better world in the midst of eternal mercies.