First Reading — Genesis 15:1-12, 17-18
Clement of Rome
On 15:5–6
Abraham, styled "the friend," [Isaiah 41:8] was found faithful, inasmuch as he rendered obedience to the words of God. He, in the exercise of obedience, went out from his own country, and from his kindred, and from his father's house, in order that, by forsaking a small territory, and a weak family, and an insignificant house, he might inherit the promises of God. For God said to him, "Get you out from your country, and from your kindred, and from your father's house, into the land which I shall show you. And I will make you a great nation, and will bless you, and make your name great, and you shall be blessed. And I will bless them that bless you, and curse them that curse you; and in you shall all the families of the earth be blessed." [Genesis 12:1-3] And again, on his departing from Lot, God said to him, "Lift up your eyes, and look from the place where you now are, northward, and southward, and eastward, and westward; for all the land which you see, to you will I give it, and to your seed forever. And I will make your seed as the dust of the earth, [so that] if a man can number the dust of the earth, then shall your seed also be numbered." [Genesis 13:14-16] And again [the Scripture] says, "God brought forth Abram, and spoke unto him, Look up now to heaven, and count the stars if you are able to number them; so shall your seed be. And Abram believed God, and it was counted to him for righteousness." [Genesis 15:5-6] On account of his faith and hospitality, a son was given him in his old age; and in the exercise of obedience, he offered him as a sacrifice to God on one of the mountains which He showed him. [Genesis 22:9]
Responsorial Psalm — Psalm 105:1-2, 3-4, 6-7, 8-9
Eusebius of Caesarea
On 104:4–5
In Psalm 104 [LXX], David, when referring to the stories of Abraham, Isaac and Jacob, the very men who were his godly ancestors, who lived before Moses' day, calls them Christs, only because they all received the outpouring of the Holy Spirit. And when he tells how they were hospitably received by foreigners, and how they learned that God was their Savior when plots were devised against them, following Moses' account, he names them prophets also and Christs, before Moses had been born and before he had laid down the rule that such men should be anointed with oil.
Gospel — Matthew 7:15-20
John Chrysostom
On 7:15
Having taught that the gate is strait, because there are many that pervert the way that leads to it, He proceeds, Take heed of false prophets. In the which that they might be the more careful, He reminds them of the things that were done among their fathers, calling them false prophets; for even in that day the like things fell out.
On 7:15
Yet He may seem here to have aimed under the title of false prophets, not so much at the heretic, as at those who, while their life is corrupt, yet wear an outward face of virtuousness; whence it is said, By their fruits ye shall know them. For among heretics it is possible many times to find a good life, but among those I have named never.
On 7:16
And a hypocrite is easily discerned; for the way they are commanded to walk is a hard way, and the hypocrite is loth to toil. And that you may not say that you are unable to find out them that are such, He again enforces what He had said by example from men, saying, Do men gather grapes of thorns, or figs of thistles?
On 7:18
But that none should say, An evil tree brings forth indeed evil fruit, but it brings forth also good, and so it becomes hard to discern, as it has a two-fold produce; on this account He adds, A good tree cannot bring forth evil fruit, neither can an evil tree bring forth good fruit.
On 7:19
He had not enjoined them to punish the false prophets, and therefore shews them the terrors of that punishment that is of God, saying, Every tree that bringeth not forth good fruit shall be hewn down, and cast into the fire. In these words He seems to aim also at the Jews, and thus calls to mind the word of John the Baptist, denouncing punishment against them in the very same words. For he had thus spoken to the Jews, warning them of the axe impending, the tree that should be cut down, and the fire that could not be extinguished. But if one will examine somewhat closely, here are two punishments, to be cut down, and to be burned; and he that is burned is also altogether cut out of the kingdom; which is the harder punishment. Many indeed fear no more than hell; but I say that the fall of that glory is a far more bitter punishment, than the pains of hell itself. For what evil great or small would not a father undergo, that he might see and enjoy a most dear son? Let us then think the same of that glory; for there is no son so dear to his father as is the rest of the good, to be deceased and to be with Christ. The pain of hell is indeed intolerable, yet are ten thousand hells nothing to falling from that blessed glory, and being held in hate by Christ.