Nicene and Post-Nicene Fathers, Vol. III:
Doctrinal Treatises of St. Augustin: Section 6

6. All these ways our Lord Jesus Christ and His Apostles used. For when it had been objected that His disciples had plucked the ears of corn on the sabbath-day, the instance was taken from history; “Have ye not read,” saith He, “what David did when he was an hungered, and they that were with him; how he entered into the house of God, and did eat the shewbread, which was not lawful for him to eat, neither for them that were with him, but only for the priests?” 1701 But the instance pertains to ætiology, that, when Christ had forbidden a wife to be put away, save for the cause of fornication, and they, who asked Him, had alleged that Moses had granted permission after a writing of divorcement had been given, This, saith He, “Moses did because of the hardness of your heart.” 1702 For here a reason was given, why that had been well allowed by Moses for a time; that this command of Christ might seem to show that now the times were other. But it were long to explain the changes of these times, and p. 350 their order arranged and settled by a certain marvellous appointment of Divine Providence.

Footnotes

Matt. 12:3, 4

Matt. 19.8