Sin will be always acting, if we be not always mortifying, we are lost creatures.

Because he is; that is, because he is an infinitely glorious, good, wise, holy, powerful, righteous, self-subsisting , self-sufficient , and all-sufficient being; the fountain and author of all being and good; the first cause, last end, and sovereign Lord of all; therefore, he is to be worshipped: therefore, are we to admire, adore, and love him; to praise, to trust and to fear him.

Sin also carries on its war by entangling the affections and drawing them into an alliance against the mind. Grace may be enthroned in the mind, but if sin controls the affections, it has seized a fort from which it will continually assault the soul. Hence, as we shall see, mortification is chiefly directed to take place upon the affections.

It is the Spirit alone that can mortify sin; he is promised to do it, and all other means without him are empty and vain. How shall he, then, mortify sin that has not the Spirit? A man may easier see without eyes, speak without a tongue, than truly mortify one sin without the Spirit.

...but let it suffice us to know that it became God, who is the supreme Ruler, Governor and Judge of all that sin should be punished with death in the sinner or his surety; and therefore if God would bring many sons to glory, the Captain of their salvation must undergo sufferings and death, to make satisfaction for them.

Let no man think to kill sin with few, easy, or gentle strokes. He who hath once smitten a serpent, if he follow not on his blow until it be slain, may repent that ever he began the quarrel. And so he who undertakes to deal with sin, and pursues it not constantly to the death.

No heart can conceive that treasury of mercies which lies in this one privilege, in having liberty and ability to approach unto God at all times, according to his mind and will.