The authority of the Law being founded and established, God delivers his First Commandment–
Thou shalt have no other gods before me.
The purport of this commandment is, that the Lord will have himself alone to be exalted in his people, and claims the entire possession of them as his own. That it may be so, he orders us to abstain from ungodliness and superstition of every kind, by which the glory of his divinity is diminished or obscured; and, for the same reason, he requires us to worship and adore him with truly pious zeal. The simple terms used obviously amount to this. For seeing we cannot have God without embracing everything which belongs to him, the prohibition against having strange gods means, that nothing which belongs to him is to be transferred to any other. The duties which we owe to God are innumerable, but they seem to admit of being not improperly reduced to four heads: Adoration, with its accessory spiritual submission of conscience, Trust, Invocation, Thanksgiving. By Adoration, I mean the veneration and worship which we render to him when we do homage to his majesty; and hence I make part of it to consist in bringing our consciences into subjection to his Law. Trust, is secure resting in him under a recognition of his perfections, when, ascribing to him all power, wisdom, justice, goodness, and truth, we consider ourselves happy in having been brought into intercourse with him. Invocation, may be defined the retaking of ourselves to his promised aid as the only resource in every case of need. Thanksgiving, is the gratitude which ascribes to him the praise of all our blessings. As the Lord does not allow these to be derived from any other quarter, so he demands that they shall be referred entirely to himself. It is not enough to refrain from other gods. We must, at the same time, devote ourselves wholly to him, not acting like certain impious despisers, who regard it as the shortest method, to hold all religious observance in derision. But here precedence must be given to true religion, which will direct our minds to the living God. When duly imbued with the knowledge of him, the whole aim of our lives will be to revere, fear, and worship his majesty, to enjoy a share in his blessings, to have recourse to him in every difficulty, to acknowledge, laud, and celebrate the magnificence of his works, to make him, as it were, the sole aim of all our actions. Next, we must beware of superstition, by which our minds are turned aside from the true God, and carried to and fro after a multiplicity of gods. Therefore, if we are contented with one God, let us call to mind what was formerly observed, that all fictitious gods are to be driven far away, and that the worship which he claims for himself is not to be mutilated. Not a particle of his glory is to be withheld: everything belonging to him must be reserved to him entire. The words, “before me,” go to increase the indignity, God being provoked to jealousy whenever we substitute our fictions in his stead; just as an unfaithful wife stings her husband’s heart more deeply when her adultery is committed openly before his eyes. Therefore, God having by his present power and grace declared that he had respect to the people whom he had chosen, now, in order to deter them from the wickedness of revolt, warns them that they cannot adopt strange gods without his being witness and spectator of the sacrilege. To the audacity of so doing is added the very great impiety of supposing that they can mock the eye of God with their evasions. Far from this the Lord proclaims that everything which we design, plan, or execute, lies open to his sight. Our conscience must, therefore, keep aloof from the most distant thought of revolt, if we would have our worship approved by the Lord. The glory of his Godhead must be maintained entire and incorrupt, not merely by external profession, but as under his eye, which penetrates the inmost recesses of his heart.
From Institutes of the Christian Religion, John Calvin, 1559