Psalms 37:31

The law of his God is in his heart - The Lord promised that a time should come in which he would make a new covenant with the house of Israel; he would put his laws in their minds, and in their hearts he would write them. This is fulfilled in the case above.

None of his steps shall slide - His holy heart always dictates to his eyes, his mouth, his hands, and his feet. The precepts which direct his conduct are not only written in his Bible, but also in his heart.

The law of his God is in his heart - That is, he loves it; he thinks of it; he makes it the inward rule of his conduct: Deuteronomy 6:6; Psalm 40:8 The word "law" here is a general term for the truth of God - for all that he has revealed to guide men. As long as that truth is in the heart; as long as it is the object of love; as long as it is suffered to guide and control us, so long will our words and conduct be right.

None of his steps shall slide - Margin, "goings." The idea is, that his course will be firm and steady. He will not fall into sin, and his life will be prosperous and happy. This is in accordance with the general sentiment in the psalm, that religion tends to promote prosperity, happiness, and length of days on the earth.

37:31 Heart - His thoughts, meditations and affections are fixed upon it. Slide - Slide, or swerve, from the rule, from God's law.