I come now to the point which (is urged both by our own brethren and by the heretics). Our brethren adduce it as a pretext for entering on curious inquiries, and the heretics insist on it for importing the scrupulosity (of their unbelief). It is written, they say, "Seek, and ye shall find." Let us remember at what time the Lord said this. I think it was at the very outset of His teaching, when there was still a doubt felt by all whether He were the Christ, and when even Peter had not yet declared Him to be the Son of God (cf Clement of Alexandria's version of Matthew 16:16 below), and John (Baptist?) had actually ceased to feel assurance about Him ... Now, the Gentiles knew nothing either of Him, or of any of His promises. Therefore it was to Israel that he spake when He said, "I am not sent but to the lost sheep of the house of Israel." (Matthew 15:24) Not yet had He "cast to the dogs the children's bread" (Matthew 15:26) not yet did He charge them to "go into the way of the Gentiles." It is only at the last that He instructs them to "go and teach all nations, and baptize them," when they were so soon to receive "the Holy Ghost, the Comforter, who should guide them into all the truth." And this, too, makes towards the the same conclusion. If the apostles, who were ordained to be teachers to the Gentiles, were themselves to have the Comforter for their teacher, far more needless was it to say to us, "Seek, and ye shall find," to whom was to come, without research, our instruction by the apostles, and to the apostles themselves by the Holy Ghost. All the Lord's sayings, indeed, are set forth for all men; through the ears of the Jews have they passed on to us. Still most of them were addressed to Jewish persons; they therefore did not constitute instruction properly designed for ourselves, but rather an example. [Tertullian De praescriptionibus aduersus haereses omnes 8.13]Clearly again this section is related to what appears in Adv Marc 4.7.5. But notice the important variant of Matthew 16:16 acknowledged not only by Tertullian's source (Justin?) and Clement:
Many (πολλοὶ) also of those who called to the Lord said, “Son of David, have mercy on me (υἱὲ ∆αβίδ, ἐλέησόν με).” A few (ὀλίγοι), too, knew Him as the Son of God (υἱὸν τοῦ θεοῦ); as Peter, whom also He pronounced blessed (ἐμακάρισεν), “for flesh and blood revealed not the truth to him, but His Father in heaven” (ὅτι αὐτῷ σὰρξ καὶ αἷμα οὐκ ἀπεκάλυψε τὴν ἀλήθειαν, ἀλλ' ἢ ὁ πατὴρ αὐτοῦ ὁ ἐν τοῖς οὐρανοῖς) —showing that the Gnostic recognises the Son of the Omnipotent, not by the eyes of the flesh conceived in the womb, but by the Father’s own powerAll our canonical gospels stress that Peter identified Jesus as the Christ and in Matthew it is Christ, the Son of God which is utterly senseless. Yet Clement makes clear here that Peter was originally rewarded for being the true Gnostic in knowing that Jesus was the Son of God. Interestingly our canonical gospels only have one scene where someone identified Jesus as 'Son of David, have mercy on me.' Secret Mark provides the other example to help establish Clement's 'many.'