Πίστει καὶ αὐτὴ Σάρρα δύναμιν εἰς καταβολὴν σπέρματος ἔλαβεν καὶ παρὰ καιρὸν ἡλικίας, ἐπεὶ πιστὸν ἡγήσατο τὸν ἐπαγγειλάμενον (Hebrews 11:11, Westcott and Hort)
The traditional translation of Hebrews 11:11 implies that it was (at least partially) Sarah's faith that allowed her to conceive. For example ESV:
By faith Sarah herself received power to conceive, even when she was past the age, since she considered him faithful who had promised.
However, I came across an argument that it is more likely Abraham's faith is in view of the writer. The crux of the argument, I think, is that δύναμιν εἰς καταβολὴν σπέρματος ἔλαβεν (roughly "received power to conceive/deposit seed") more naturally refers to the male role of reproduction than the female role.
The NIV footnotes offer a not-very-literal translation that captures this alternative understanding:
By faith Abraham, even though he was too old to have children—and Sarah herself was not able to conceive—was enabled to become a father because he considered him faithful who had made the promise
Likewise the NET Bible has:
By faith, even though Sarah herself was barren and he was too old, he received the ability to procreate, because he regarded the one who had given the promise to be trustworthy.
There is a significant textual variant,
Πίστει καὶ αὐτὴ Σάρρα στεῖρα δύναμιν εἰς καταβολὴν σπέρματος ἔλαβεν καὶ παρὰ καιρὸν ἡλικίας, ἐπεὶ πιστὸν ἡγήσατο τὸν ἐπαγγειλάμενον
listed in NA27 and elevated to the main reading in NA28 that might lend support to the alternate understanding. Textus Receptus (Stephanus) has a ἔτεκεν after ἡλικίας, which probably does not affect much.
What is the original reading and whose faith is more likely to be in view of the author? Is there any evidence about which sex a phrase like δύναμιν εἰς καταβολὴν σπέρματος ἔλαβεν would be more refer to in period writing? How likely is it that the writer of Hebrews would attribute a miracle to Sarah's faith based on the rest of the letter, the Genesis account, and the culture in which he wrote?