Here it is, Ignatius to the Magnesians 11:

11.1 Ταῦτα δέ, ἀγαπητοί μου, οὐκ ἐπεὶ ἔγνων τινὰς ἐξ ὑμῶν οὕτως ἔχοντας, ἀλλʼ ὡς μικρότερος ὑμῶν θέλω προφυλάσσεσθαι ὑμᾶς μὴ ἐμπεσεῖν εἰς τὰ ἄγκιστρα τῆς κενοδοξίας, ἀλλὰ πεπληροφορῆσθαι71 ἐν τῇ γεννήσει καὶ τῷ πάθει καὶ τῇ ἀναστάσει τῇ γενομένῃ ἐν καιρῷ τῆς ἡγεμονίας Ποντίου Πιλάτου· πραχθέντα ἀληθῶς καὶ βεβαίως ὑπὸ Ἰησοῦ Χριστοῦ, τῆς ἐλπίδος ἡμῶν, ἧς ἐκτραπῆναι μηδενὶ ὑμῶν γένοιτο. (IgnMag 11)

Holmes, M. W. (1999). The Apostolic Fathers : Greek texts and English translations (Updated ed.) (156). Grand Rapids, Mich.: Baker Books.

Here's Ehrman's translation:

I am not writing you these things, my beloved, because I have learned that some of you are behaving like this. But as one who is less important than you I want to protect you from being snagged by the fish hooks of worthless ideas. You should be fully convinced of the birth and suffering and resurrection that occurred in the time of the governor Pontius Pilate. These things were truly and certainly done by Jesus Christ, our hope. From this hope may none of you turn away. (IgnMag 11)

Here Ignatius is responding to a danger that the Magnesians may fall prey to: that of Judaizing and perhaps even elevating Judaism above Christianity. Ignatius reminds them to focus on Christ: "You should be fully convinced ..."

The other picture in here that draws my attention is that of the "fish hooks of worthless ideas". Others (Holmes, Lake, Lightfoot) translate this as "hooks", but "fish hooks" seems more appropriate (cf. BDAG). Have you ever been fishing and snagged the fish instead of hooking it in the mouth? I have. Ignatius is saying, "don't let the false ideas draw you in—don't be caught up in them." On the metaphor, Schoedel includes a helpful footnote in his commentary on Ignatius' letters (helpfully copied/pasted from the Logos version!):

For the metaphorical use of the word “hooks” (fishhooks) see Diogenes Laertius 4.47; Plutarch De virt. moral. 6, 446a; Aristaenetus Ep. 1.17; cf. Lucian Pisc. 47. From the same circle of metaphors comes the word “lure” used in Jas 1:14 (cf. Plutarch De ser. num. vind. 10, 554f). For the full development of the imagery in connection with heresy see Theodoret Hist. eccl. 5.13.6.

Schoedel, W. R., Ignatius, S., Bishop of Antioch, & Koester, H. (1985). Ignatius of Antioch : A commentary on the Letters of Ignatius of Antioch. Includes indexes. (129) Hermeneia—a critical and historical commentary on the Bible. Philadelphia: Fortress Press.