9 For the sacrifice was not properly the setting to rights of Isaac, but of Abraham who also offered, and by that was tried. Thus God accepted the will of the offerer, but prevented that which was offered from being sacrificed. For the death of Isaac did not procure freedom to the world, but that of our Saviour alone, by whose stripes we all are healed. For He raised up the falling, healed the sick, satisfied those who were hungry, and filled the poor, and, what is more wonderful, raised us all from the dead; having abolished death, He has brought us from affliction and sighing to the rest and gladness of this feast, a joy which reaches even to heaven.
For not we alone are affected by this, but because of it, even the heavens rejoice with us, and the whole church of the firstborn, written in heaven, is made glad together, as the prophet proclaims, saying, 'Rejoice, you heavens, for the Lord has had mercy upon Israel. Shout, you foundations of the earth. Cry out with joy, you mountains, you high places, and all the trees which are in them, for the Lord has redeemed Jacob, and Israel has been glorified.' And again; 'Rejoice, and be glad, you heavens; let the hills melt into gladness, for the Lord has had mercy on His people, and comforted the oppressed of the people.'
Source: Letters (New Advent)