Parah 7:3-4
Parah 7:3
If a person mixed the water with one hand and performed some other task with his other hand, the water is invalid if he mixed it for himself but valid if he mixed it for someone else. If he mixed the water for both himself and for someone else, his is invalid and the other person’s is valid. If he mixed the water for two others at the same time, both are valid.
Parah 7:4
If one person told another, “Mix the water for me and I’ll mix it for you,” the first one mixed is valid (because no other task interrupts its preparation). If one person told another, “Collect the water for me and I’ll collect it for you,” the second water collected is valid (again because no other task interrupts its preparation). If one person told another, “Mix the water for me and I’ll collect it for you,” both are valid. If he said, “Collect the water for me and I’ll mix the water for you,” both are invalid.