Ablution is an essential practice as a Muslim because it is a requirement to perform a prayer. A Muslim approximately utilizes 25 liters of water for five daily prayers. Islam categorized greywater produced from ablution as Musta'mal water. Recent studies show significant amount of greywater produced in some of the university's mosque in Malaysia. However, most of these studies proposed on reusing ablution water for plant irrigation and toilet flushing but few mentioned its use for ablution purpose. To address this issue, a recycling device is designed to filter and treat the Musta'mal water which subsequently is used back for ablution purpose. This approach promotes sustainable ablution practices and was based on Hadiths, ljma' and Qiyas. Field tests were carried out in university's mosque via a small scale model to gather sufficient information prior to the construction of a full-scale recycling device, which is called ReWudhuk. Samplings of treated and untreated Musta'mal water are carried out in six different days. Laboratory tests were conducted to analyze their pH value, turbidity (NTU), color changes (TCU), total suspended solids (TSS), and amount of dissolved oxygen (DO). Experimental results indicated that Musta'mal water quality conform Malaysian Drinking Water Quality Standard (DWQS) requirements, and was comparably better than the typical water tap quality. A successful trial run results via the small scale device leads into the development of ReWudhuk. It was designed ergonomically based on PEI score, where it integrates ablution place and filtering systems into a compact device with dimensions of 90 cm height and 50 cm circumference. ReWudhuk was designed for retrofitting purpose since it was common for a mosque or musolla to have an ablution water tank. Conceptually, ReWudhuk is feasible to be produced not only from Islamic perspective, but also from the engineering aspect.