I found this story:

Even Belh´s Dogs...

Şakik-i Belhi, may Allah be merciful to him, once went to Mecca.

Someone recognized him and came close to him.

- Efendim, could you give me a piece of advice?

Belh asked that person:

- How is your livelihood? If you cannot find anything what do you do?

The man answered:

- If we find something we are thankful, if we cannot find a thing we are patient.

Belh then offered his teaching:

- Even Belh´s dogs can do this. If they find something they eat, if they don´t they wait patiently.

The man got surprised and asked:

- Well then efendim, what do you do?

- When we get something we give it to our religious fellows. When we don´t we do not feel sad. We thank our Lord.

This advice very much appealed to the poor man. He hugged Belhi and said:

- Efendim, you are a blessed man. May Allah Ta´ala increase your prosperity.

Belh is said the name of the city where Rumi was born. I don´t think that there is a special idiomatic meaning on it. Belh´in köpekleri means The dogs of Belh. It is just to express that ´even dogs do this, what is the difference between them and you people? you must do more than this´

oh..I see..thank you very much..for the beginning I thought the same thing but after a bit of thinking I supposed it can be something special, like an idiom..thank you again caliptrix