I’ve not read a ton about the Sufis, but anytime I do, I always find particular gems like this:

These words mean nothing except to the initiated! Beware! Do not say, “I have understood.” The more you understand and grasp these words, the farther you will be from understanding them. Their meaning comes in not understanding. All your troubles, misfortunes and disappointments arise from such understanding. This understanding is a chain for you. You must escape it to gain anything at all.

This other page has a good introductory overview to Sufism, along with a bunch of sayings by notable Sufis. And I have an older post about the use of “teaching stories” among the Sufi tradition.