In the words of the Prophet Micah (6:8 MT):
הִגִּ֥יד לְךָ֛ אָדָ֖ם מַה־טֹּ֑וב וּמָֽה־יְהוָ֞ה דֹּורֵ֣שׁ מִמְּךָ֗ כִּ֣י אִם־עֲשֹׂ֤ות מִשְׁפָּט֙ וְאַ֣הֲבַת חֶ֔סֶד וְהַצְנֵ֥עַ לֶ֖כֶת עִם־אֱלֹהֶֽיךָ׃
The word הַצְנֵעַ is most generally translated “humbly,” but the Hebrew word has more layers to it than that. This same root (צָנַע) also means “modestly” or “reservedly.”  How does it change the reading to use this rendering?
“He has told you, O man, what is good and what YHWH requires of you: just doing justice, and loving covenant loyalty, and modestly walking with your G-d.”
If humility and modesty are so closely related, that should reflect in how we present ourselves publicly. We should be dressing as for an audience with YHWH Himself, in His throne room.
A pertinent question to ask in defining “modesty/humility” is what is not modest or humble. Tim Kelly of Season of our Joy answers that question, “Anything that draws attention to yourself.”  That answer applies to both men and women. Anything we do that takes the attention away from others and directs it to ourselves is worship-thievery. We are stealing worship that is due only to the Almighty by misappropriating it to ourselves.
Paul Nison suggests, “Anything we expose, we advertise… but not for sale. We advertise it as ‘free for the taking.'”  The present author can see where that statement could be taken to an extreme, e.g. requirements that every body part be covered, including covering the face, veiling the eyes, gloving the hands, etc. As that extreme is not in view in the culture whence the Bible comes, it would be a supererogatory demand. It is also important to note that there is a greater responsibility on the part of the viewer to exercise self-control, though a responsibility not to stumble our brother or sister, as Nison observes, should inform our decisions on how we present ourselves.
In a culture where there was limited selection in attire, the issue of modesty dealt less with exposed midriffs, cleavage, and undergarments in Biblical times and more with ostentatious dress. In fact, jewelry (1 Timothy 2:9; 1 Peter 3:3), elaborate hairstyles (ibid.), expensive clothing (ibid.), extra-long tzitziyot (Matthew 23:5), and extra large tefillin/phylacteries (ibid.) are specifically mentioned in the Biblical discussions. Thus, wearing an Armani suit or a large diamond would be just as immodest (Biblically) as wearing a bikini to a worship service would.
There is a mutual responsibility for men and women — yes, both — to guard the purity of one another, both in how we present ourselves to one another, and in how we act toward one another… regardless of how they present (Song of Songs).
Psalm 119:133 jps
:פְּעָמַי הָכֵן בְּאִמְרָתֶךָ וְאַל-תַּשְׁלֶט-בִּי כָל-אָוֶן
“Order my footsteps by Thy word;
and let not any iniquity have dominion over me.”
- s.v. “צָנַע,” Francis Brown, S.R. Driver, & Charles A. Briggs, The Brown-Driver-Briggs Hebrew and English Lexicon (Boston, Mass.: Houghton & Mifflin, 1906), 857.
- Tim Kelly, “Modesty and the Hebrew Roots Movement” (interview), TorahLife.tv (1 Oct 2013), 1:12-1:38.
- Paul Nison, “What Happened to Modesty?” (video), Modesty: An Issue of the Heart.