All things therefore are of one and the same substance…

““All things therefore are of one and the same substance, that is, from one and the same God; as also the Lord says to the disciples “Therefore every scribe, which is instructed unto the kingdom of heaven, is like unto a man that is an householder, which bringeth forth out of his treasure things new and old.” He did not teach that he who brought forth the old was one, and he that brought forth the new, another; but that they were one and the same. For the Lord is the good man of the house, who rules the entire house of His Father; and who delivers a law suited both for slaves and those who are as yet undisciplined; and gives fitting precepts to those that are free, and have been justified by faith, as well as throws His own inheritance open to those that are sons. And He called His disciples “scribes” and “teachers of the kingdom of heaven;” of whom also He elsewhere says to the Jews: “Behold, I send unto you wise men, and scribes, and teachers; and some of them ye shall kill, and persecute from city to city.” Now, without contradiction, He means by those things which are brought forth from the treasure new and old, the two covenants; the old, that giving of the law which took place formerly; and He points out as the new, that manner of life required by the Gospel, of which David says, “Sing unto the Lord a new song;” and Esaias, “Sing unto the Lord a new hymn. His beginning (initium), His name is glorified from the height of the earth: they declare His powers in the isles.” And Jeremiah says: “Behold, I will make a new covenant, not as I made with your fathers” in Mount Horeb. But one and the same householder produced both covenants, the Word of God, our Lord Jesus Christ, who spake with both Abraham and Moses, and who has restored us anew to liberty, and has multiplied that grace which is from Himself.””

— The Church Fathers