Analysis:

This quatrain by Saadi Shirazi delves into the nature of love and human relationships. Let's break down the lines:

Line 1: آن را که نظر به سوی هر کس باشد

"The one whose gaze wanders to everyone,"
This line refers to a person who is fickle and easily distracted, who doesn't focus their attention or affection on one person.

Line 2: در دیدهٔ صاحبنظران خس باشد

"In the eyes of the discerning, is considered worthless."
Those who can see beyond the surface understand that such a person is not worthy of deep connection or commitment.

Line 3: قاضی به دو شاهد بدهد فتوی شرع

"A judge gives a legal ruling based on two witnesses,"
This line is a reference to Islamic law, where two witnesses are required to prove a claim.

Line 4: در مذهب عشق شاهدی بس باشد

"But in the religion of love, one witness is enough."
In contrast to the legal system, love is a personal experience that needs no external validation. The experience of love itself is sufficient proof.

Deeper Meaning:

This quatrain suggests that:

Love is a matter of the heart: Love is not based on external factors like societal rules or the opinions of others.
Focus is essential in love: True love requires focus and commitment to one person.
The experience of love is its own proof: Love is a personal experience that cannot be quantified or measured by external standards.

This quatrain celebrates the unique and personal nature of love, suggesting that it is a matter of the heart and not of legal or societal rules. It also highlights the importance of focus and commitment in a loving relationship.