.....For Adam, with all the innumerable advantages he had, that is, all helps necessary in himself; and no opposition or difficulty from himself to conflict with, utterly broke the original covenant.  But believers who have very little strength in themselves, and have a powerful inbred opposition to their stability, are yet secured in their station by the interposition of their divine sponsor.  Farther:  we need a surety, because in the state and condition of sin we are not capable of immediate dealing or covenanting with God.  It could not be on account of God's holiness and glorious greatness, that there should be any new covenant at all between God and sinners, without the interposition of a surety.  Nor did it become the infinite wisdom of God, after man had broken and disannulled the covenant made with him in innocency, to enter into a new covenant with him in his fallen condition, without an immediate undertaker, that it should be assuredly kept and the ends of it attained.  If you have lent a man a thousand pounds upon his own security, when, his circumstances were good, and he hath not only failed in his payment, but contracted other debts innumerable, will you lend him ten thousand pounds on the same security, expecting to receive it again?  Wherefore, God knowing our inability, laid help upon one that is mighty, he exalted one chosen from among the people.  (Psalms 89:19.)  He committed this work to Jesus Christ, and then said concerning us, 'now deliver them, for I have found a ransom.'......
                                                                                                                                   John Owen, D. D.