“Submit to one another out of reverence for Christ” (Eph 5:21).
This 11-page chapter (available for free as a PDF) concisely and convincingly explains why the phrase “mutual submission” is unhelpful at best:
Wayne Grudem, “The Myth of Mutual Submission as an Interpretation of Ephesians 5:21,” in Biblical Foundations for Manhood and Womanhood
(ed. Wayne Grudem; Foundations for the Family Series; Wheaton: Crossway, 2002), 221–31.