Jesus said the first and greatest commandment is this: Love the Lord your God with all your heart, with all your soul, and with all your mind” (Mt. 22:37 NET). This commandment is echoed in the OT and in the NT. When discussing this great commandment, Charles Hodge related it to religion, morality, and Romans 1:18ff. I’ve put his comments on this below, although it’s longer than my usual post. However, it’s pretty easy to read and very insightful. I’ve edited the layout slightly:
The preëminence of this commandment is further evident from the fact that religion, or the duty we owe to God, is the foundation of morality. Without the former, the latter cannot exist.
This is plain,
(1.) From the nature of the case. Morality is the conformity of an agent’s character and conduct to the moral law. But the moral law is the revealed will of God. If there be no God, there is no moral law; and if a man does not acknowledge or recognize God, there is no higher law than his own reason to which he can feel any obligation to be conformed.
(2.) It is a principle of our nature that if a man disregard a higher obligation, he will not be controlled by a lower. This principle was recognized by our Lord when He said, “He that is faithful in that which is least, is faithful also in much; and he that is unjust in the least, is unjust also in much.” (Luke 16:10.) This involves the converse: He that is unfaithful in much, is unfaithful in that which is least.
(3.) It is the testimony of experience that where religion has lost its hold on the minds of the people, there the moral law is trampled under foot. The criminal and dangerous class in every community consists of those who have no fear of God before their eyes.
(4.) It is the secret conviction of every man that his duty to God is his highest duty, as is evinced by the fact that the charge of atheism is one from which the human soul instinctively recoils. It is felt to be a charge of the utter degradation, or of the deadness of all that is highest and noblest in the nature of man.
(5.) The most decisive and solemn evidence of this truth, however, is to be found in the revealed purpose of God to forsake those who forsake Him; to give up to the unconstrained control of their evil passions, those who cast off their allegiance to Him. The Apostle says of the heathen world that it was “Because that when they knew God, they glorified him not as God, neither were thankful, … God gave them up unto vile affections.” (Rom. 1:21, 26.) And again in ver. 28, “As they did not like to retain God in their knowledge, God gave them over to a reprobate mind, to do those things which are not convenient; being filled with all unrighteousness, fornication, wickedness, covetousness, maliciousness; full of envy, murder, debate, deceit, malignity; whisperers, backbiters, haters of God, despiteful, proud, boasters, inventors of evil things, disobedient to parents, without understanding, covenant breakers, without natural affection, implacable, unmerciful.” Such are the natural, the actual, the inevitable, and the judicially ordained effects of men’s refusing to retain God in their knowledge.
Notwithstanding all this we see multitudes of men of whom it may be said that God is not in all their thoughts. They never think of Him. They do not recognize his providence. They do not refer to his will as a rule of conduct. They do not feel their responsibility to Him for what they think or do. They do not worship Him; nor thank Him for their mercies. They are without God in the world. Yet they think well of themselves. They are not aware of the dreadful guilt involved in thus forgetting God, in habitually failing to discharge the first and highest duty that rests on rational creatures. Self-respect or regard to public opinion often renders such men decorous in their lives. But they are really dead while they live; and they have no security against the powers of darkness.
It is painful also to see that scientific men and philosophers so often endeavour to invalidate the arguments for the existence of God, and advance opinions inconsistent with Theism; arguing, as they in many cases do, to prove either that there is no evidence of the existence of any power in the universe other than of physical force, or that no knowledge, consciousness, or voluntary action can be predicated of an infinite Being. This is done in apparent unconsciousness that they are undermining the foundations of all religion and morality; or that they are exhibiting a state of mind which the Scriptures pronounce worthy of reprobation.
Charles Hodge, Systematic Theology, vol. 3 (Oak Harbor, WA: Logos Research Systems, Inc., 1997), 279–281.
Covenant Presbyterian Church (OPC)
Hammond, WI, 54015