Analysis:
This quatrain by Saadi Shirazi is a beautiful exploration of dreams, desire, and the fleeting nature of pleasure. Let's break down each line:

Line 1: من دوش قضا یار و قدر پشتم بود

"Yesterday, fate was my friend and destiny my support,"
The speaker begins by setting the scene of a dream, where fate seemed to be on their side. It suggests a night filled with hope and optimism.

Line 2: نارنج زنخدان تو در مشتم بود

"The bitterness of your smile was clasped in my grasp."
This line introduces a paradox. While the smile is usually associated with joy, the speaker describes it as "bitter". This could suggest unfulfilled desire, a sense of longing, or perhaps a realization of the impermanence of pleasure.

Line 3: دیدم که همی گزم لب شیرینش

"I saw how your sweet lips moved and stirred,"
The speaker continues to describe the dream, focusing on the object of their desire. The image of "sweet lips" suggests a sensual and passionate experience.

Line 4: بیدار چو گشتم سر انگشتم بود

"But when I awoke, it was only my finger I'd stirred."
The final line brings the dream to a sudden and disappointing end. The speaker realizes that the intense emotions and sensations they experienced were merely illusions created by their subconscious mind.

Deeper Meaning:

This quatrain explores themes of desire, dreams, and the nature of reality. It suggests that:

Dreams can be both joyful and painful: The speaker's dream is filled with both pleasure and a sense of longing.
The line between reality and fantasy is blurred: The speaker's experience highlights the difficulty of distinguishing between dreams and waking life.
Pleasure is fleeting: The beauty and joy of the dream are quickly replaced by the harsh reality of waking up.

This quatrain serves as a reminder of the ephemeral nature of human desires and the power of the human mind to create vivid and compelling fantasies. It invites the reader to contemplate the relationship between dreams and reality.