Kamasutra 2.9.26

2.9.26

tad etat tu na kāryam/ samayavirodhād asabhyatvāc ca/ punar api hy āsāṃ vadanasaṃsarge svayam evārtiṃ prapadyeta/ ity ācāryāḥ//

The Acharyas (i.e., ancient and venerable authors) are of opinion that this Auparishtaka is the work of a dog and not of a man, because it is a low practice, and opposed to the orders of the Holy Writ, and because the man himself suffers by bringing his lingam into contact with the mouths of eunuchs and women. But Vatsyayana says that the orders of the Holy Writ do not affect those who resort to courtezans, and the law prohibits the practice of the Auparishtaka with married women only. As regards the injury to the male, that can be easily remedied.