Analysis:

This quatrain by Saadi Shirazi presents a complex interplay of love, war, and the human heart. Let's break down each line:

Line 1: آن کودک لشکری که لشکر شکند

"That child of war who shatters armies"
This line refers to a powerful warrior, capable of defeating large armies. The image of a child is juxtaposed with the image of a warrior, suggesting a paradoxical combination of youth and strength.

Line 2: دایم دل ما چو قلب کافر شکند

"Continually shatters our hearts like a non-believer's"
Here, the beloved is compared to a warrior who shatters hearts, just as easily as they might shatter armies. The comparison to a "non-believer's heart" suggests a heart that is hardened or unyielding.

Line 3: محبوب که تازیانه در سر شکند

"The beloved, who wields a whip in his head"
This line is more metaphorical. The "whip in the head" could symbolize the powerful impact the beloved has on the lover's heart or mind. It might also suggest a sense of control or dominance.

Line 4: به زانکه ببیند و عنان برشکند

"Is better than one who sees and yet reins in his passion"
This line contrasts the beloved who freely expresses their emotions with someone who suppresses their feelings. The implication is that it's better to be passionate and open, even if it causes pain, than to hide one's emotions.

Deeper Meaning:

This quatrain explores the themes of love, power, and the human condition. It suggests that:

Love can be both destructive and exhilarating: The beloved is portrayed as both a powerful force and a source of great pain.
Passion is better than restraint: The speaker values the intensity of the beloved's passion, even though it may cause suffering.
The heart can be a battlefield: The heart is depicted as a place of conflict, where love and pain coexist.

This quatrain is a complex and evocative exploration of the human experience. It suggests that love, like war, can be both beautiful and destructive.