Shiva Purana
सप्तैव तानि वर्षाणि चतुर्वर्णायुतानि च ॥ भगवन्तं सदा शंभुं यजंते विविधैर्मखैः ॥ ३७ ॥
All the seven Varṣas contain people of the four castes. They worship lord Śiva always with various kinds of sacrifices.
english translation
saptaiva tAni varSANi caturvarNAyutAni ca ॥ bhagavantaM sadA zaMbhuM yajaMte vividhairmakhaiH ॥ 37 ॥
hk transliteration by Sanscript