Saadi was an important Persian poet and a sufi (mystic) who lived in Persia in 13. century. His well known works are Bostan (The Orchard) and Gulistan (The Rose Garden). Many figurative stories were told by him about Islamic and universal virtues in his works. These two works of him were taught as lessons in the schools of Ottoman Empire for many centuries. 

U.S. President Barack Obama quoted Saadi´s Gulistan in a videotaped Nowruz (New Year´s) greeting to the Iranian people in March 2009: "There are those who insist that we be defined by our differences. But let us remember the words that were written by the poet Saadi, so many years ago: ´The children of Adam are limbs to each other, having been created of one essence.(1)

Here are some verses of him translated by me:

How can he know; he doesn´t ask?
He would know if he asked.
How can he ask; he doesn´t know?
He would ask if he knew.

I don´t say you not to sail to the sea,
"If you will sail, bear even the flood" I say.

The origin of men is one (same),
It is the mutual foundation layed in creation.
It is enough for one of us to feel pain,
That pain is all of us.

If you look at without love even Joseph(2) is ugly.
If you look at Devil with love you think he is an angel.

Heart is more valuable than Kaaba; if Kaaba is a home built by Abraham, heart is a place God looks at.

Even ten dervishes fit into one carpet, but two king don´t fit into one palace.

Don´t forget the bee which has honey in his mouth has a sting on its tail.

(1) http://en.wikipedia.org/wiki/Saadi_(poet)#His_works
(2) A prophet who was famous with his good looking.