Job 31:12

For it is a fire that consumeth to destruction - This may mean that such an offence would be a crime that would provoke God to send destruction, like a consuming fire upon the offender (Rosenmuller and Noyes), or more likely it is designed to be descriptive of the nature of the sin itself. According to this, the meaning is, that indulgence in this sin tends wholly to ruin and destroy a man. It is like a consuming fire, which sweeps away everything before it. It is destructive to the body, the morals, the soul. Accordingly, it may be remarked that there is no one vice which pours such desolation through the soul as licentiousness. See Rush on the Diseases of the Mind. It corrupts and taints all the fountains of morals, and utterly annihilates all purity of the heart. An intelligent gentleman, and a careful observer of the state of things in society, once remarked to me, that on coming to the city of Philadelphia, it was his fortune to be in the same boarding-house with a number of young men, nearly all of whom were known to him to be of licentious habits. He has lived to watch their course of life; and he remarked, that there was not one of them who did not ultimately show that he was essentially corrupt and unprincipled in every department of morals. There is not any one propensity of man that spreads such a withering influence over the soul as this; and, however it may be accounted for, it is certain that indulgence in this vice is a certain evidence that the whole soul is corrupt, and that no reliance is to be placed on the man’s virtue in any respect, or in reference to any relation of life.

And would root out all mine increase - By its desolating effects on my heart and life. The meaning is, that it would utterly ruin him; compare Luke 15:13, Luke 15:30. How many a wretched sensualist can bear testimony to the truth of this statement! How many a young man has been wholly ruined in reference to his worldly interests, as well as in reference to his soul, by this vice compare Proverbs 7: No young man could do a better service to himself than to commit the whole of that chapter to memory, and so engrave it on his soul that it never could be forgotten.