And you shall eat the old harvest, and clear out the old because of the new.
Read Chapter 26
Ambrose of Milan
There ought to be a concurrence of the old and the new, as in the case of the Old and New Testament. It is written, “Eat the oldest of the old store and, new coming on, cast away the old.” Let our food be knowledge of the patriarchs. Let our minds banquet in the prophetic books of the prophets. Such nourishment should our minds partake of, the truth of the body of Christ, and not just the external appearance of a lamb. Our eyes should not be affected by the shadow cast by the law. Rather, the clear grace of the Lord’s passion and the splendor of his resurrection should illuminate our vision. .
And we eat the oldest of the old [grain] when we retain in our hearts the sweet memory of the old commandment which was given to the human race from the beginning, by loving the Lord our God with all our heart, all our soul and all our strength, and by loving our neighbor as ourselves. And we cast away the old [to make room] for the new that is coming on when we cease to keep the typic statutes of the Mosaic law according to the letter but keep these same statutes quite gladly as they are understood through the Spirit. Our hearts [are] being renewed in the hope of the heavenly kingdom in accordance with that [saying] of the apostle: “If then anyone is in Christ a new creature, the old things have passed away; behold, things have been made new,” and [with that saying] in the Apocalypse: “And he that sat upon the throne said, ‘Behold, I make all things new.’ “
Old; Being unable to consume all. (Menochius)
Hebrew, "ye shall eat old store, and bring forth the old because of the new. "Septuagint, "you shall eat the old of old, and you shall bring out the old from the face of the new. "Like a householder, who bringeth forth out of his treasury new things and old, Matthew xiii. 52. (Haydock)