I like to peruse Cramer’s Catenae Graecorum Patrum from time to time. This is a collection of comments made on the NT by several important early church writers, compiled and edited over the years. The name means “Chain of Greek Fathers,” alluding to the way the comments from different writers are chained together.
The text can be conveniently accessed via the Diogenes reader, or in a variety of other places online.
As I’m preparing to preach through 1 John, I have been dipping in Catena in epistulam Joannis i (that’s the catena for 1 John) recently. Just as a little exercise, I have translated the introductory section to the book of 1 John. The Greek in the catenae ranges from easy to quite difficult, depending on the interpreter. One common difficulty is the need to “fill in the blanks.” In true commentary style, the text is sparse and often portions of the comments have been edited out (which you can go back and look at, especially in the portions from John Chrysostom where we have his longer homilies extant), requiring some guessing. Not to mention that Patristic Greek, while sharing a lot of affinity with the Koine, is also its own animal. All that to say, here is the introduction to Catena in the Epistle of 1 John. I have made little effort to create smooth English syntax. The Greek itself is quite choppy.
Catena in the Epistle of 1 John: Introduction
Afterwards, John himself, having written the gospel, he also sent this epistle, reminding those who already believe in the Lord. And chiefly just as in the Gospel, so also he theologizes in this epistle concerning the Logos, showing that he is always in God, and teaching that the Father is light, so that we may know the Logos as the radiance from him.
While teaching of God, he expounds that the mystery concerning us is not of recent origin; rather it is from the beginning and is/exists eternally, and now has been revealed in the Lord, who is eternal life and true God.
And he lays out the reason for his Parousia and epiphany, teaching that it is as follows: for the purpose of destroying the works of the Devil, and to free us from death, and that we may come to know the Father and his Son, our Lord Jesus Christ.
Indeed he writes to all ages—to children, to young men, and to old men—that God has been made known, and that the devilish activities have been conquered, when death was abolished. In addition, throughout the entire Epistle he teaches concerning love, wanting us to love one another, and showing that it is necessary to love one another, since Jesus also loved us.
Also, he explains concerning the difference between fear and love, and children of God and children of the Devil, and concerning deadly sin and non-deadly sin, and the difference between spirits. And in addition he distinguishes that some spirits are from God, and some are spirits of error; and when we know/recognize children of God, and when of the devil; and how concerning some sins we ought to pray for the sinners, and concerning other sins we ought not to pray; and that the one not loving their neighbor is not worthy of the call, nor are they able to be reckoned as belonging to Christ. And he shows the unity of the Son to the Father, and that the one denying the Son does not have the Father.
He makes a distinction in this epistle saying that the distinguishing feature of the Antichrist is this: saying Jesus is not the son himself, the Christ. [here there is a short ἵνα clause which has to date defied my attempts to unravel it]
He encourages throughout the entire epistle that those who believe in the Lord not loose heart if they are hated by the world, but rather that they rejoice because the world’s hatred shows that the believers have been transferred from this word and are, at the last, citizens of heaven. And in the end of the epistle, he again calls to memory saying that the Son of God is heavenly life and True God, and so that we serve him and guard ourselves from idols
 It is unclear to me how best to render the Greek καθ’ ἡμάς here. Taking καθ’ ἡμάς as “concerning/about us” is a standard way it is used in both NT and Greek at large. But it is not clear to me what this would meaning this context.
 In the Greek, τὸ μυστήριον is the assumed subject carried through from the prior infinitive phrase. This would expect a neuter pronoun, αὐτό, rather than the αὐτόν which is in the text. An accusative masculine here would have no immediate antecedent, but could make sense as a reference to Jesus. LSJ notes, though, that the neut. sg. sometimes is αὐτόν (see also Cambridge Greek Lexicon). This understanding works well and has been adopted here.
 The Greek verb τυγχάνω here approximates γίνομαι/εἰμί with an existential sense. This usage is noted in E. A. (Evangelinus Apostolides) Sophocles, Joseph Henry Thayer, and Henry Drisler, Greek Lexicon of the Roman and Byzantine Periods (From B.C. 146 to A.D. 1100) (New York: C. Scribner’s sons, 1900), http://archive.org/details/cu31924021609395.