Shiva Purana
चतुर्ष्वपि च यामेषु मूर्तीनां च चतुष्टयम् ॥ कृत्वावाहनपूर्वं हि विसर्गावधि वै क्रमात् ॥ ३९ ॥
There are also four idols in the four Yamas Before making the invocation, one should perform the rituals in order until the end of the discharge.
english translation
caturSvapi ca yAmeSu mUrtInAM ca catuSTayam ॥ kRtvAvAhanapUrvaM hi visargAvadhi vai kramAt ॥ 39 ॥
hk transliteration by Sanscript