Charles Spurgeon Commentary Deuteronomy 6:9-12

"And thou shalt write them upon the door-posts of thy house, and upon thy gates. And it shall be, when Jehovah thy God shall bring thee into the land which he sware unto thy fathers, to Abraham, to Isaac, and to Jacob, to give thee, great and goodly cities, which thou buildest not, and houses full of all good things, which thou filledst not, and cisterns hewn out, which thou hewedst not, vineyards and olive-trees, which thou plantedst not, and thou shalt eat and be full; then beware lest thou forget Jehovah, who brought thee forth out of the land of Egypt, out of the house of bondage." — Deuteronomy 6:9-12 (ASV)

And you shall write them upon the posts of your house, and on your gates. And it shall be, when the LORD your God shall have brought you into the land which he swore to your fathers, to Abraham, to Isaac, and to Jacob, to give you great and goodly cities, which you did not build, and houses full of all good things, which you did not fill, and wells digged, which you did not dig, and vineyards and olive trees, which you did not plant; when you shall have eaten and are full, then beware lest you forget the LORD, which brought you forth out of the land of Egypt, from the house of bondage.

Pride is the peculiar sin of prosperity, and pride stands side by side with forgetfulness of God.

Instead of remembering from where our mercies came, we begin to thank ourselves for these blessings, and God is forgotten. I remember one of whom it was said that he was a self-made man, and he adored his Creator; and I may say that there are a great many persons who do just that. They believe that they have made themselves, and so they worship themselves. Let us remember that it is God who gives us strength to get wealth or to get position, and, therefore, to him be all the honor of it, and never let him be forgotten.