Answer
(Fatwa: 670/562=D/1430)
How did you come to know that it is not permissible? Give the reference.
It is better to keep it at clean place, but if someone kept it in toilet, it cannot be termed as unlawful; since doing zikr is the practice of miswak, the nature of which is known to Allah only. Thus, every thing does zikr of Allah in his own way and every thing of the world is included in the meaning of the verses:
وان من شئ الا یسبح بحمدہ، یسبح لہ ما فی السماوات وما فی الارض
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband