Charles H. Spurgeon on Psalms 119:11

Thy word have I hid in mine heart. This saying, to hide, imports that David studied not to be ambitious to set forth himself and to make a glorious show before men; but that he had God for a witness of that secret desire which was within him. He never looked to worldly creatures; but being content that he had so great a treasure, he knew full well that God who had given it him would so surely and safely guard it, as that it should not be laid open to Satan to be taken away. Saint Paul also declareth unto us (1 Timothy 1:19) that the chest wherein this treasure must be hid is a good conscience. For it is said, that many being void of this good conscience have lost also their faith, and have been robbed thereof. As if a man should forsake his goods and put them in hazard, without shutting a door, it were an easy matter for thieves to come in and to rob and spoil him of all; even so, if we leave at random to Satan the treasures which God hath given us in his word, without it be hidden in this good conscience, and in the very bottom of, our heart as David here speaketh, we shall be spoiled thereof. John Calvin.