The first non-canonical instalce of a “rule of faith” appears twice in the writing of Ignatius of Antioch. The first, shown below, is in his Epistle to the Trallians, ch 9 (additional material that appears in the longer Greek recension is included below in brackets). The second instance appears in his letter to the Christians at Smyrna.

Be deaf, therefore, when any would speak to you apart from (at variance with) JESUS CHRIST
[the Son of God],
who was descended from the family of David,
born of Mary,
who truly was born
[both of God and of the Virgin …
truly took a body; for the Word
became flesh and dwelt among us
without sin …],
ate and drank [truly],
truly suffered persecution under Pontius Pilate,
was truly [and not in appearance]
crucified and died …
who was also truly raised from the dead [and rose after three days],
his Father raising him up …
[and after having spent forty days with the Apostles,
was received up to the Father,
and sits on his right hand,
waiting till his enemies are put under his feet].

Κωφώθητε οὖν, ὅταν ὑμῖν χωρὶς Ἰησοῦ Χριστοῦ λαλῇ τις
[τοῦ υἱοῦ τοῦ Θεοῦ]
τοῦ ἐκ γένους [γενομένου] Δαβὶδ
τοῦ ἐκ Μαρίας,
ὃς ἀληθῶς ἐγεννήθη
[καὶ ἐκ θεοῦ καὶ ἐκ παρθένου …
ἀληθῶς ἀνέλαβε σῶμα· ὁ Λόγος
γὰρ σὰρξ ἐγένετο καὶ ἐπολιτεύσατο
ἄνευ ἁμαρτίας …],
ἔφαγέν τε καὶ ἔπιεν [ἀληθῶς],
ἀληθῶς ἐδιώχθη ἐπὶ Ποντίου Πιλάτου,
ἀληθῶς [δὲ, καὶ οὐ δοκήσει] ἐσταυρώθη
καὶ ἀπέθανεν …
ὃς καὶ ἀληθῶς ἠγέρθη ἀπὸ νεκρῶν [καὶ ἀνέστη διὰ τριῶν ἡμερῶν],
ἐγείροντος αὐτὸν τοῦ Πατρὸς αὐτοῦ …
[καὶ τεσσαράκοντα ἡμέρας συνδιατρίψας τοῖς Ἀποστόλοις,
ἀνελήφθη πρὸς τὸν Πατέρα·
καὶ ἐκάθισεν ἐκ δεξιῶν αὐτοῦ,
περιμένων ἕως ἄν τεθῶσιν οἱ ἐχθροὶ αὐτοῦ ὑπὸ τοὺς πόδας αὐτοῦ].

From Schaff, Creeds V.II P.11-12

For those who are curious, here is the version from Smyr.:
Smyr. 1:1   I glorify Jesus Christ, the God who made you so wise, for I observed that you are established in an unshakable faith, having been nailed, as it were, to the cross of the Lord Jesus Christ in both body and spirit, and firmly established in love by the blood of Christ, totally convinced with regard to our Lord that he is truly of the family of David with respect to human descent, Son of God with respect to the Divine will and power, truly born of a virgin, baptized by John in order that all righteousness might be fulfilled by him, 2 truly nailed in the flesh for us under Pontius Pilate and Herod the tetarch (from its fruit we derive our existence, that is, from his divinely blessed suffering), in order that he might raise a banner for the ages through his resurrection for his saints and faithful people, whether among Jews or among Gentiles, in the one body of his church.
Smyr. 2:1   For he suffered all these things for our sakes, in order that we might be saved;[98] and he truly suffered just as he truly raised himself—not, as certain unbelievers say, that he suffered in appearance only (it is they who exist in appearance only!). Indeed, their fate will be determined by what they think: they will become disembodied and demonic.
Smyr. 3:1   For I know and believe that he was in the flesh even after the resurrection; 2 and when he came to Peter and those with him, he said to them: “Take hold of me; handle me and see that I am not a disembodied demon.” And immediately they touched him and believed, being closely united with his flesh and blood. For this reason they too despised death; indeed, they proved to be greater than death. 3 And after his resurrection he ate and drank with them like one who is composed of flesh, although spiritually he was united with the Father.

Tral. 9:1 Κωφώθητε οὖν, ὅταν ὑμῖν χωρὶς Ἰησοῦ Χριστοῦ λαλῇ τις, τοῦ ἐκ γένους Δαυίδ, τοῦ ἐκ Μαρίας, ὅς ἀληθῶς ἐγεννήθη, ἔφαγέν τε καὶ ἔπιεν, ἀληθῶς ἐδιώχθη ἐπὶ Ποντίου Πιλάτου, ἀληθῶς ἐσταυρώθη καὶ ἀπέθανεν, βλεπόντων τῶν [98] ἐπουρανίων καὶ ἐπιγείων καὶ ὑποχθονίων· 2 ὅς καὶ ἀληθῶς ἠγέρθη ἀπὸ νεκρῶν, ἐγείραντος αὐτὸν τοῦ πατρὸς αὐτοῦ, ὅς καὶ κατὰ τὸ ὁμοίωμα [99] ἡμᾶς τοὺς πιστεύοντας αὐτῷ οὕτως ἐγερεῖ ὁ πατὴρ αὐτοῦ ἐν Χριστῷ Ἰησοῦ, οὗ χωρὶς τὸ ἀληθινὸν ζῆν οὐκ ἔχομεν.