The law of his God is in his heart; none of his steps shall slide. -Psalm 37:31
Put the law into the heart, and the whole man is right. This is where the law should be; for then it lies, like the tables of stone in the ark, in the place appointed for it. In the head it puzzles, on the back it burdens, in the heart it upholds.
What a choice word is here used, “the law of his God”! When we know the Lord as our own God His law becomes liberty to us. God with us in covenant makes us eager to obey His will and walk in His commands. Is the precept my Father’s precept? Then I delight in it.
We are here guaranteed that obedient-hearted man shall be sustained in every step that he takes. He will do that which is right, and he shall therefore do that which is wise. Holy action is always the most prudent, though it may not at the time seem to be so, We are moving along the great highroad of God’s providence and grace when we keep to the way of His law. The Word of God has never misled a single soul yet; its plain directions to walk humbly, justly, lovingly, and in the fear of the Lord are as much words of wisdom to make our way prosperous as rules of holiness to keep our garments clean. He walks surely who walks righteously.
[from Faith’s Checkbook by Charles H. Spurgeon]