Peace and Good!
Many of the early heresies in the Church rejected the Old Testament. They considered it too messy, both in the actions of the people involved and the images of God they found there. Yet, the Church held onto the Old Testament as a vital part of the scriptures, both fulfilled in the Gospels and illuminating them.
St. Irenaeus had to fight against an understanding of faith that was too cerebral: the Gnostics, who proposed that salvation involved 'knowing (gnosis)' and escape from the flesh. Yet, the Word becoming flesh is central to the Gospel message. Irenaeus knew that, and fought to articulate a theology which did not ignore sin, but more importantly did not try to explain away the Incarnation nor the redemption of the body.
Christian conversion is a balancing act, recognizing the reality of sin but in the context of the goodness of all creation, including the body. Weak was we are, balancing these two things is not always easy. Francis himself struggled with it. How to be austere so as to grow in grace, not become some disembodied ghost. Part of his secret was to begin always with praise of God and the goodness of creation. All creation: the sun and the moon, as well as the rocks and the worms and even that part of creation we flee: death. Sister Death.
I conclude with a beautiful quote from St. Irenaeus' Against Heresies:
Since you are the work of God, wait patiently for the hand of your Artist, who does all things at the right time. Present to him a supple and docile heart, and keep the form that this Artist gave you, having in yourself the water that comes from him and without which you would become hard and would reject the imprint of his fingers.By letting yourself be formed by him, you will rise to perfection, for through this art of God, the clay that is in you will be hidden; his hand created your substance… But if you become hard and push away his art and show that you are discontent with the fact that he made you a human being, by your ingratitude towards God you will have rejected not only his art but life itself; for it is the very nature of God’s goodness to form, and to be formed is the very nature of being human. Thus, if you give yourself to him by giving him your faith in him and your submission, you will receive the benefit of his art and you will be God’s perfect work. If on the contrary, you resist him and if you flee from his hands, the cause of your incompleteness will be in yourself who did not obey, and not in him. (Against the Heresies IV, Pr 4; 39,2)
God bless you!