An important indication of Sarah's status and position as well as of her own forceful character is the fact that, although she was Abraham's wife and worked alongside him, she acted independently of him when circumstances required.
We do not have here a man, the focal personality, around whom the action revolved, and the acquiescent or passive woman caught up in his orbit.
More than this, it is obvious that, on several occasions, Abraham not only respected Sarah as his wife but also felt the need to turn to her for counsel and guidance or admitted an obligation to obtain her agreement before making a decision.
We also see that from time to time Abraham acted not on his own initiative but upon instructions from Sarah, sometimes of his own volition, and–in one specific, unique instance–at the express command of God: "In all that Sarah hath said unto thee, hearken unto her voice" (Genesis 21:12).
–Rabbi Adin Steinsaltz
From Biblical Images by Rabbi Adin Steinsaltz