Najis mughallazah from pigs and dogs can cause several health problems (zoonosis); special methods are needed for cleaning under Islamic law, namely using water and soil. Bentonite, as a type of soil with good adsorbing ability, can be used as thaharah media, while kefir whey containing lactoferrin functions as an antimicrobial. The purpose of this research is to formulate whey kefir and bentonite into a liquid soap preparation as an antiseptic agent for najis mughallazah, determine the physical characteristics of whey kefir liquid soap with bentonite, and test its antibacterial activity against one of the pathogens found in dog saliva, namely Staphylococcus aureus bacteria. Data were analyzed using one-way ANOVA. The type of this research is a laboratory experiment with 4 bentonite concentration variation formulas, namely F0 (without bentonite), F1 (bentonite 2 g), F2 (bentonite 4 g), and F3 (bentonite 6 g). The research results show that bentonite and whey kefir can be formulated as liquid soap that has suspension characteristics in physical appearance. The difference in bentonite concentration significantly affects soap characteristics such as organoleptic, pH, viscosity, sedimentation volume, and dispersibility. Evaluation of the second formula (F2) with a bentonite concentration of 2 g is the best concentration because it has characteristics that match SNI (06-4085-1996). Bentonite concentration is not recommended below 2 gr, because the resulting pH tends to be less alkaline, and bentonite concentration is not recommended to exceed 6 gr because it will cause excess sedimentation volume. The formulation with the highest inhibition zone is formulation 3 (22.3 mm), the criteria for inhibition (strong), and the formulation with the lowest inhibition zone is formulation 0 (6.6 mm), the criteria for inhibition (very weak).