It has been read in two ways: as fass and as fiss. The reading as fass is more correct. (Bustan, 40)
The word fass is used in this book (Fusūs) in four senses. First: fass means 'word'. This is expressed as follows: The fass of every ḥikma (wisdom) is the word attributed to it. The word fass is the subject (mubtadā), and the word 'word' is the predicate (khabar). Just as the bezel of a ring is a part of the ring, so too the world is completed by its existence. In this sense, the spirits (arwāḥ) of the prophets are like the bezel of the ring, and their corporeal existences are like the ring in relation to the bezel.
Second: fass means qalb (the heart). Here, too, the word fass is made the subject, and the phrase 'in a word' is the predicate, and by the phrase 'the fass of inspired wisdom', and then by listing the other fass, this is ishāra (an allusion) to it. After this, by making fass the subject and veiling the expression 'in a word' (i.e., by bringing a particle before the predicate), the intention was to make the predicate implicit. In this case, the hearts (qulūb) of the prophets are like the bezel of the ring, and their spirits are like the ring in relation to the bezel.
Third: fass means ḥikma, that is, the sciences engraved upon their spirits. Regarding their fass-i khātam (the seal fass), you may say, as he says, that it is the hearts upon which wisdoms are revealed. Accordingly, their knowledge is like the bezel of the ring, and their spirits are like the ring in relation to the bezel. This is alluded to by the saying: In everything I have witnessed from it, there is a divine wisdom entrusted to us. Although the Fusūs book uses fass in the sense of ḥikma, it does not specify the number of wisdoms.
Fourth: fass is the essence of ḥikma. This is explained as follows: The first thing the Master gives to His servant is the essence of divine wisdom... At that time, the essence is like the bezel of the ring, and wisdom is like the ring in relation to the bezel. With these four meanings, the intended purpose of the analogy—namely, to indicate the cycle of wujūd (existence) through all its levels—has been achieved. (Sofyavi, 11)