This is not how Greek grammar functions. Any time the collective is addressed you will find a plural pronoun is used; for example: Matt. 25:24 ὁ βασιλεὺς ἐρεῖ αὐτοῖς· ἀμὴν λέγω ὑμῖν - "And the King will say to them, truly I say to you... ." Here, ὑμῖν - 'you', 'all of you', or 'each of you' is dative second person plural. John 6:53 εἶπεν οὖν αὐτοῖς ὁ Ἰησοῦς ἀμὴν ἀμὴν λέγω ὑμῖν - "Therefore Jesus said to them, truly truly I say to you... ." I can show you numerous examples of this type of construction. This is certainly not the same structure you find in our text in Hebrews 10.
An example of a singular address is John 13:38 - ἀμὴν ἀμὴν λέγω σοι - "Truly truly I say to you... ." σοι is the dative case second person singular pronoun 'to you'.
I cannot think of an example where the collective is ever addressed with a singular pronoun. I could be wrong. If you can find such an example I would be interested in it.
An example of a singular address is John 13:38 - ἀμὴν ἀμὴν λέγω σοι - "Truly truly I say to you... ." σοι is the dative case second person singular pronoun 'to you'.
I cannot think of an example where the collective is ever addressed with a singular pronoun. I could be wrong. If you can find such an example I would be interested in it.
My apologies. The reference was supposed to be Romans !0, not Hebrews 10.