This is the 18242nd most frequent Russian word.
чистыми
"Чистыми" means "net" or "clean" in the sense of "clear of deductions" or "pure."
In this sentence, 'чистыми' is an instrumental plural form of 'чистый' and is used to describe the state in which the 'rooms' were left.
Мы оставили комнаты чистыми.
We left the rooms clean.
Here, 'чистыми' describes the 'hands' used for handling the laundry, emphasizing their state of cleanliness.
Я люблю своё бельё чистыми руками.
I love handling my laundry with clean hands.
In this case, 'чистыми' refers to the state of the children upon returning home, using the instrumental plural form to describe them.