Analysis:

This quatrain by Saadi Shirazi is a beautiful expression of devotion and fear.

Submissive Love: The speaker expresses a deep devotion to the beloved, offering to become dust beneath their feet. This is a common trope in Persian poetry, symbolizing complete surrender and self-abasement in love.
Fear of Rejection: While the speaker is willing to sacrifice everything for the beloved, they also express a deep fear of rejection. The fear of the beloved stepping on their head symbolizes the fear of being trampled upon or disregarded.
The Power of Love: The quatrain highlights the immense power of love, capable of both elevating and crushing the lover.

Themes:

Devotion and Submission: The central theme is the speaker's complete devotion to the beloved and their willingness to sacrifice everything.
Fear and Insecurity: The quatrain explores the fear of rejection and the insecurity that often accompanies deep love.
The Power of Love: The poem highlights the transformative power of love and its ability to both inspire and devastate.

Deeper Meaning:
This quatrain is a poignant exploration of the human experience of love. It captures the complex emotions that accompany deep devotion, including the fear of rejection and the willingness to sacrifice everything for the beloved. The image of the speaker as dust beneath the beloved's feet is a powerful metaphor for the vulnerability and humility of love.

This quatrain is a timeless expression of the human heart, capturing the beauty and pain of love.