Theodoros of Samothrace, fr. 1 (FGrH 62; Photius, Bibl. 190, 152b26)
“In the seventh book [Ptolemy Chennos reports that] Theodôros of Samothrace says that after Zeus was born he laughed without stopping for seven days. This is why the number seven is thought to be “final” [or whole, complete”]
ἐν δὲ τῶι ζ̄ περιέχεται ὡς Θεόδωρος ὁ Σαμοθρὰιξ τὸν Δία φησὶ γεννηθέντα ἐπὶ ἑπτὰ ἡμέρας ἀκατάπαυστον γελάσαι· καὶ διὰ τοῦτο τέλειος ἐνομίσθη ὁ ἑπτὰ ἀριθμός.
Alexander of Aphrodisias, Probl. 2.47:
“The number seven, as Pythagoras insists, is complete in nature. The mathematicians and musicians agree too. But eight is incomplete.”
ὁ ἑπτὰ ἀριθμὸς τέλειός ἐστι τῇ φύσει, ὡς μαρτυρεῖ Πυθαγόρας καὶ οἱ ἀριθμητικοὶ καὶ οἱ μουσικοί• ὁ δὲ ὀκτὼ ἀτελής
These references come from Ken Dowden’s entry in Brill’s New Jacoby (62 F1). The following does not: