Hebrews 6:13-16
“For when God made promise to Abraham, because He could swear by no greater, He swore by Himself, saying, Surely blessing I will bless you, and multiplying I will multiply you. And so after he had patiently endured, he obtained the promise. For men verily swear by the greater, and an oath for confirmation is to them an end of all strife.”
1. Having boldly reflected on the faults of the Hebrews, and sufficiently alarmed them, he consoles them, first, by praises, and secondly (which also is the stronger ground), by the [thought] that they would certainly attain the object of their hope. Moreover he draws his consolation, not from things future, but again from the past, which indeed would the rather persuade them. For as in the case of punishment, he alarms them rather by those [viz. things future], so also in the case of the prizes [set before them], he encourages them by these [viz. by things past], showing [herein] God's way of dealing. And that is, not to bring in what has been promised immediately, but after a long time. And this He does, both to present the greatest proof of His power, and also to lead us to Faith, that they who are living in tribulation without having received the promises, or the rewards, may not faint under their troubles.
And omitting all [the rest], though he had many whom he might have mentioned, he brought forward Abraham both on account of the dignity of his person, and because this had occurred in a special way in his case.
And yet at the end of the Epistle he says, that “all these, having seen the promises afar off, and having embraced them, received them not, that they without us should not be made perfect.” “For when God made promise to Abraham” (he says) “because He could swear by no greater, He swore by Himself, saying, Surely blessing I will bless you, and multiplying I will multiply you. And so after he had patiently endured, he obtained the promise.” How then does he say at the end [of the Epistle] that “he received not the promises,” and here, that “after he had patiently endured he obtained the promise”? How did he not receive? How did he obtain? He is not speaking of the same things in this place and in the other, but makes the consolation twofold. God made promises to Abraham, and after a long space of time He gave the things [spoken of] in this place, but those others not yet.
“And so after he had patiently endured, he obtained the promise.” Do you see that the promise alone did not effect the whole, but the patient waiting as well? Here he alarms them, showing that oftentimes a promise is thwarted through faintheartedness. And this he had indeed shown through [the instance of] the [Jewish] people: for since they were faint-hearted, therefore they obtained not the promise. But now he shows the contrary by means of Abraham. Afterwards near the end [of the Epistle] he proves something more also: [viz.] that even though they had patiently endured, they did not obtain; and yet not even so are they grieved.
2. “For men verily swear by the greater, and an Oath for confirmation is to them an end of all strife. But God because He could swear by no greater, swore by Himself.” Well, who then is He that swore unto Abraham? Is it not the Son? No, one says. Certainly indeed it was He: however, I shall not dispute [thereon]. So when He [the Son] swears the same oath, “Verily, verily, I say unto you,” is it not plain that it was because He could not swear by any greater? For as the Father swore, so also the Son swears by Himself, saying, “Verily, verily, I say unto you.” He here reminds them also of the oaths of Christ, which He was constantly uttering. “Verily, verily, I say unto you, he that believes in Me shall never die.”
What is, “And an oath for confirmation is to them an end of all strife”? It is instead of, “by this every doubtful question is solved”: not this, or this, but every one.
Source: Homilies on the Epistle to the Hebrews (New Advent)