Analysis:
This quatrain by Saadi Shirazi is a poignant expression of deep love and heartbreak. The speaker is conveying a sense of profound loss and longing, comparing their love to a flood that has overwhelmed them.

Line 1: بگذشت و چه گویم که چه بر من بگذشت

"It has passed, and what can I say of what has happened to me?"
The speaker reflects on a past event, perhaps a loss or separation from their beloved, and expresses their inability to fully articulate the depth of their pain.

Line 2: سیلاب محبتم ز دامن بگذشت

"The flood of my love has overflowed from my heart."
This line uses a powerful metaphor to convey the overwhelming nature of the speaker's love. The image of a flood suggests that their love was so intense that it could not be contained.

Line 3: دستی به دلم فرو کن ای یار عزیز

"Place your hand on my heart, O dear beloved,"
The speaker invites their beloved to witness the extent of their suffering. This is a plea for understanding and empathy.

Line 4: تا تیر ببینی که ز جوشن بگذشت

"So that you may see the arrow that has pierced through my armor."
This line suggests that the speaker has been deeply wounded by love, and that this wound is hidden beneath a protective exterior. The image of an arrow piercing through armor implies a deep and lasting pain.

Themes explored in the quatrain:
Love and loss: The quatrain explores the pain of losing a loved one or being separated from them.
Heartbreak: The speaker's emotional turmoil is vividly portrayed through the metaphor of a flood and an arrow piercing the heart.
Longing and yearning: The speaker expresses a deep longing for their beloved and a desire for their return.

This quatrain is a moving expression of heartbreak and the enduring power of love. The speaker's vulnerability and emotional intensity make this a particularly poignant and memorable verse.