The poet begs his mistress not to wound him with her eyes but to hurt him directly with harsh words, as her glances are more lethal than her cruelty.
The poem distinguishes between two kinds of violence: the tongue (direct language) and the eye (glance). The eye's power comes from its indirectness, its deniability—she can always claim she meant nothing. Line 6 reveals that she deliberately 'turns' her eyes away, making her cruelty an act. Yet this deliberate glance wounds him more than deliberate words could. Her aesthetic power is greater than her verbal power; she wounds through presence (and absence) more than through speech.
Lines 4 and 7 emphasize power imbalance: her might exceeds his defense. The poem asks her to use less of her power—speak rather than glance, wound less rather than more. This is a plea for mercy grounded in her overwhelming strength. Yet his excuse for her (line 9) reveals his need to believe in her agency and intentionality. If her cruelty were accidental, his love would be fool's gold. He needs her to be deliberately cruel, to confirm she knows what she's doing.
Like asking someone to just break up with you directly instead of slowly ghosting you. The indirect cruelty—the look that signals rejection—is somehow more devastating than explicit rejection. You're begging for mercy through honesty.