From the letter, the infidelity of beauty has emerged; such is the depth of our suffering.

This couplet captures the profound agony of realizing that the very beauty you adore is also the source of your suffering. Mir Taqi Mir suggests that the 'infidelity of beauty' (bewafai-e-husn) has emerged from the letter itself. It's a heartbreaking thought: that the perfection you admire is fundamentally deceptive, leading to an unavoidable punishment for the lover.