Translation:He does not heat that, because it is already hot.
So in Hebrew you do? I'm almost positive you wouldn't in English, in fact googling it immediately turned up you usually don't unless the meaning would be unclear without it. http://www.quickanddirtytips.com/education/grammar/when-to-use-a-comma-before-because
I'm an amateur writer and actually am having trouble thinking of a time I've ever written a comma before because. This is different in Hebrew though?
Asking grammar questions the native speakers can't even answer. Haha. I am not clear on the rule in English except that if anything I'm guessing people are more likely to leave it out even if needed. Definitely struck me as odd in this sentence. I'm hoping a grammar geek will drop by eventually maybe and teach us some easy to remember rule about commas before because.
In English, you never use a comma when the independent clause (one that could stand alone) is followed by a dependent one. Dependent clauses usually start with the words: when, where, while, as, since, if, although, because. Here is a devide to help you remember the words: www_asia_because.
She went to the store because she needed milk.
He listened to music while he completed his homework.
HOWEVER, if the independent clause comes first, you DO need a comma.
Because she needed milk, she went to the store.
While he completed his homework, he listened to music.
A comma goes before a conjunction joining independent clauses (clauses that can stand as complete sentences). Think of it as a comma + conjunction = a period. If this sentence could be broken into two complete sentences ("He is not heating that. It is already hot."), then the comma before the word joining them is perfectly legitimate.