Is zakah valid if a person pays it to discharge an obligation he owes?

The questioner : And so we said regarding the athar of al-Hasan: "Be lenient in the zakah of wounds."

The Shaykh : The zakah of the roots.

The questioner : All of it is black, meaning. Yes. It was he

The Shaykh : Like it, if it is permissible for the upper, it is permissible for the lower.

The questioner : And you have children and black slaves.

The Shaykh : No, pay attention to this issue; it is necessary to be aware of it. Zakah is not valid if a person pays it to discharge an obligation he owes. This is the rule: it is not valid if he pays it to discharge an obligation he owes. For example, if he has a brother whom he is obligated to support, and he wants to give his zakah to his brother, it is not valid, because if he gives him the zakah, he saves himself from the obligation of support.
So the rule is that anyone who discharges an obligation he owes by means of zakah, it is not valid for him. Is that clear? Likewise, if a guest comes to him and he feeds him from the dates and counts that as zakah, it is not valid for him, because he paid off an obligation on himself. Likewise, if he has a poor father and he is wealthy, and he wants to give his father from the zakah because of his poverty so that he can spend on himself from it, that is not valid for him, because he is obligated to support his father.
But if he pays off a debt on his father, exactly, it is valid. The reason? No, no, no, here, because he is not obligated to pay off his father's debt. And it is said the same regarding camels: if he has a poor son and he is wealthy, and the son needs support with camels, it is not permissible for him to spend on him from the zakah. But if an accident happens to him and he is held liable for a fine, it is permissible for his father to pay this fine, because he is not obligated to pay a fine on behalf of his son.