No Other Gods.

The first commandment concerns the object of our worship, Jehovah, and him only: Thou shalt have no other gods before me. The Egyptians, and other neighbouring nations, had many gods, the creatures of their own fancy, strange gods, new gods; this law was prefixed because of that transgression, and, Jehovah being the God of Israel, they must entirely cleave to him, and not be for any other, either of their own invention or borrowed from their neighbours. This was the sin they were most in danger of now that the world was so overspread with polytheism, which yet could not be rooted out effectually but by the gospel of Christ. The sin against this commandment which we are most in danger of is giving the glory and honour to any creature which are due to God only. Pride makes a god of self, covetousness makes a god of money, sensuality makes a god of the belly; whatever is esteemed or loved, feared or served, delighted in or depended on, more than God, that (whatever it is) we do in effect make a god of. This prohibition includes a precept which is the foundation of the whole law, that we take the Lord for our God, acknowledge that he is God, accept him for ours, adore him with admiration and humble reverence, and set our affections entirely upon him. In the last words, before me, it is intimated, That we cannot have any other God but he will certainly know it. There is none besides him but what is before him. Idolaters covet secresy; but shall not God search this out?

That it is very provoking to him; it is a sin that dares him to his face, which he cannot, which he will not, overlook, nor connive at. See Psalm 44:20, 21. - Matthew Henry