Two limestone monoliths, interpreted as altars, were found in the Judahite shrine at Tel Arad. Unidentified dark material preserved on their upper surfaces was submitted for organic residue analysis at two unrelated laboratories that used similar established extraction methods. On the smaller altar, residues of cannabinoids such as Δ9-teterahydrocannabinol (THC), cannabidiol (CBD) and cannabinol (CBN) were detected, along with an assortment of terpenes and terpenoids, suggesting that cannabis inflorescences had been burnt on it. Organic residues attributed to animal dung were also found, suggesting that the cannabis resin had been mixed with dung to enable mild heating. The larger altar contained an assemblage of indicative triterpenes such as boswellic acid and norursatriene, which derives from frankincense. The additional presence of animal fat―in related compounds such as testosterone, androstene and cholesterol―suggests that resin was mixed with it to facilitate evaporation. These well-preserved residues shed new light on the use of 8th century Arad altars and on incense offerings in Judah during the Iron Age.