Justin Martyr interprets the "Son of Man" title from Daniel 7 to be a prophecy of the virginal conception.
Justin Martyr, Dialogue with Trypho 76.1, in Gregory R. Lanier, Corpus Christologicum: Texts and Translations for the Study of Jewish Messianism and Early Christology (Peabody, MA: Hendrickson Academic: An Imprint of Hendrickson Publishing Group, 2021), 628 (Logos ed.)
Ὅταν γὰρ ὡς υἱὸν ἀνθρώπου λέγῃ Δανιὴλ τὸν παραλαμβάνοντα τὴν αἰώνιον βασιλείαν, οὐκ αὐτὸ τοῦτο αἰνίσσεται; τὸ γὰρ ὡς υἱὸν ἀνθρώπου εἰπεῖν, φαινόμενον μὲν καὶ γενόμενον ἄνθρωπον μηνύει, οὐκ ἐξ ἀνθρωπίνου δὲ σπέρματος ὑπάρχοντα δηλοῖ. καὶ τὸ λίθον τοῦτον εἰπεῖν ἄνευ χειρῶν τμηθέντα, ἐν μυστηρίῳ τὸ αὐτὸ κέκραγε· τὸ γὰρ ἄνευ χειρῶν εἰπεῖν αὐτὸν ἐκτετμῆσθαι, ὅτι οὐκ ἔστιν ἀνθρώπινον ἔργον, ἀλλὰ τῆς βουλῆς τοῦ προβάλλοντος αὐτὸν πατρὸς τῶν ὅλων θεοῦ.
For whenever Daniel says “one like a son of man” who was receiving the eternal kingdom, does he not hint at this? For in saying “one like a son of man,” he discloses that the one appearing became a man, but evidently not of human offspring. And in saying “a stone having been cut without hands,” he proclaimed the same thing in mystery; for to say he was “cut without hands,” it is not a human work, but one of the will of the Father and God of all things, who brought him forth.