How can the dust beneath your feet ever come into one's hands, unless an elixir is written in someone's destiny?

The poet plays brilliantly with the word 'khaak', using it both in the colloquial sense of 'nothing at all' and as the literal dust beneath the beloved's feet. The sentiment here is one of total devotion: even the humble dust touched by the beloved is not ordinary dirt, but as priceless and transformative as an alchemical elixir. Unless one has the rarest good fortune written into their destiny, achieving closeness to even the lowest trace of the beloved remains an impossible dream.