If a person is aware that masturbation is haraam, but is unaware that it invalidates the fast, does he break the fast if he masturbates during the day in Ramadan?

Dear Brothers & Sisters,
As-Salaamu-Alaikum wa Rahmatullahi wa Barakatuh. (May Allah's Peace, Mercy and Blessings be upon all of you)
One of our brothers/sisters has asked this question:
Does what the fuqaha’ say about knowledge being a condition of something breaking the fast mean that the individual should be aware of the prohibition, or be aware that it breaks the fast? This is in reference to masturbation. There is a person who does not know that masturbation is haraam, and another who knows that it is haraam, but he does not know that it breaks the fast. Which of them breaks the fast if he masturbates?
(There may be some grammatical and spelling errors in the above statement. The forum does not change anything from questions, comments and statements received from our readers for circulation in confidentiality.)
Check below answers in case you are looking for other related questions:
Ruling on rinsing the mouth whilst fasting
He woke up during the day in Ramadan and found that he was emitting maniy (semen), and he does not know whether it was a wet dream or masturbation; what is the ruling on his fast?

Answer:

Praise be to Allah

The guideline on that ignorance which excuses a person and means that he is not breaking the fast if he commits an action that is deemed to break the fast is ignorance of the prohibition and ignorance of the fact that this thing breaks the fast. 

If a person is unaware of the prohibition on masturbation and is unaware of the fact that masturbation breaks the fast, then his fast is not invalidated if he masturbates during the day in Ramadan. 

But if a person is aware of the prohibition on masturbation, but he is unaware that masturbation breaks the fast, then he has no excuse, because he is required to avoid masturbation as soon as he knows that it is prohibited. If he does not refrain from it, this is indicative of heedlessness and transgression on his part, so his fast is invalidated thereby. 

Shaykh Abu Bakr ad-Dimyaati (may Allah have mercy on him) said: “And not knowing also that it invalidates the fast” i.e., he is unaware of the prohibition and is unaware of the fact that it breaks the fast. 

In other words, he is not excused for his ignorance unless he is unaware of both points, and this is the case. If he was not ignorant of both, such as if he knows the ruling on one of them, but not the other, then he is not to be excused, because it was incumbent upon him, once he knew that it is haraam, even if he did not know that it invalidates the fast – or vice versa – to  refrain from that deed. 

I‘aanat at-Taalibeen (2/260) 

Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said: We must understand the difference between ignorance of the ruling and ignorance of what results from that ruling: 

Ignorance of the ruling means that the person is excused and there are no consequences to his action. 

Ignorance of what results from the ruling means that what is obligatory is not waived. For example, if a man has intercourse during the day in Ramadan, knowing that it is haraam, but not knowing that the severe expiation is required for it, then the expiation is not waived in his case, and he must offer expiation. But if he thought that there was nothing wrong with it, i.e., that there was no prohibition on this action, then he is not obliged to do anything.

End quote from Fataawa Noor ‘ala ad-Darb by Ibn ‘Uthaymeen (11/2) 

And Allah knows best.

Whatever written of Truth and benefit is only due to Allah's Assistance and Guidance, and whatever of error is of me. Allah Alone Knows Best and He is the Only Source of Strength.
Your brother and well wisher in Islam

Related Answers:
He had intercourse with his wife without ejaculating during the day in Ramadaan, because he was unaware that this is haraam, and he did not have a bath afterwards
If water gets inside the body whilst doing istinja’
Does not wearing hijab invalidate the fast?
Ruling on rinsing the mouth whilst fasting
He woke up during the day in Ramadan and found that he was emitting maniy (semen), and he does not know whether it was a wet dream or masturbation; what is the ruling on his fast?

Recommended answers for you:
Delaying Fajr prayer until the sun has almost risen
Dealing with a Bad Temper
The virtue of patience
When is it permissible for a woman to uncover her face?
What is the ruling on a man having intercourse with his pregnant wife?