κατὰ τὸ ῥῆμά σου
also in Luke 1:38
εἶπεν δὲ Μαριάμ, Ἰδοὺ ἡ δούλη κυρίου· γένοιτό μοι κατὰ τὸ ῥῆμά σου. καὶ ἀπῆλθεν ἀπ' αὐτῆς ὁ ἄγγελος. esv.org/Luke+1/
and I bet it builds on Deuteronomy 8 cited in Matthew 4:4,
ὁ δὲ ἀποκριθεὶς εἶπεν, Γέγραπται, Οὐκ ἐπ' ἄρτῳ μόνῳ ζήσεται ὁ ἄνθρωπος, ἀλλ' ἐπὶ παντὶ ῥήματι ἐκπορευομένῳ διὰ στόματος θεοῦ.
Verily I say unto you, This generation shall not pass, till all these things be fulfilled. Heaven and earth shall pass away, but my words shall not pass away.