P46 is very interesting at Heb 3.7, as can be seen in this picture. The original text of what the Holy Spirit says is presented as EAN THC FWNHC MOU.
Now it might just be possible to think of P46 as writing EAN THC FWNHC MOU AUTOU AKOUCHTE. Indeed this could be a conflate reading (since EAN THC FWNHC MOU AKOUCHTE is found in a single minuscule, 1319 I think). But I think Royse is spot on here (not only because he confirmed my instinctive interpretation of it), in seeing MOU as corrected by the scribe in the act of writing, with dots, deletion and a pause for thought (which happens after other corrections in P46) before the correct reading AUTOU. The agreement with 1319 is coincidental (or at least not genealogical).
But it is interesting that the scribe's instinct was to write MOU. This suggests that the scribe is an active participant in the representation of his text: thinking along with the text. Thinking aloud about what the Holy Spirit is saying. Perhaps he does not at first recognise this as an OT citation. Or perhaps he did recognise it and anticipated the first person pronouns to follow ('my ways ... my wrath ... my rest', v10f). Who knows.
But the process is controlled by his desire to present accurately the text of his exemplar, hence the correction. See the detail here: