Mistress Van Licks and her friends wanted to make sure that this slave drank their saliva. They were humiliating him for being incompetent and that is why they chose to use their saliva to do it. The mistresses collected their saliva in a glass jar and they made him drink all of it. They also spat on his face for good measure. It was humiliating and it served its purpose.
This slave was too nosy for these mistresses and they had to humiliate him to make him learn not to do what he had done. The mistresses felt that using spit to dominate him was the best way to punish him and that is why they did not hesitate to do it. They cruelly stood over him and rained spit on his face and into his mouth. His work was to swallow, to lick and to smear it on his face.
This slave had pissed off his mistresses and they had to teach him a lesson. The mistresses agreed to dominate him with spit. He was made to drink it after the mistresses collected it in a glass. He wished that they had beat him instead of degrading him with spit. But it was not optional and he had to drink it all. He was also used as a human ashtray.