Is it permissible to receive the repayment of a loan from a friend, knowing that the source of the money is from a barber's income?

It is permissible for the creditor to accept his debt from the money of a debtor whose income is predominantly from illicit (haram (definition)) sources, because the prohibition is not attached to the money itself but to the liability of its acquirer. Scholars have differed regarding the ruling on recovering a debt from the debtor's illicit money, due to the disagreement over whether the prohibition (haram) attaches to the money itself or to the liability of its acquirer.

The opinions of the scholars are summarized as follows: 1. The opinion that it is permissible to take it legally, not as a matter of piety (according to Muhammad ibn al-Hasan (definition) from the Hanafites). 2. The opinion that it is permissible to take it if the permissible (halal (definition)) portion of the money is predominant (according to Ibn al-Qasim from the Malikites). 3. The opinion that it is not permissible to take it at all, because if the illicit (haram) mixes with the permissible (halal), it renders the entire sum illicit (according to Ibn Wahb and Asbagh from the Malikites). 4. The opinion that differentiates between cases: if the creditor knows that the money was taken by theft or usurpation from a specific owner (then it is not permissible to take it, because it is the right of another), or if the money is from illicit earnings whose specific owner is unknown, such as the earnings of a singer, or money acquired through usury or gambling (then it is permissible to take it, because the claim is established against the liability of the one who acquired it, not against the money itself).

The preponderant opinion is the last differentiation; therefore, it is not permissible to take the debt from money stolen or usurped from a specific owner, whereas it is permissible to take it from illicit money whose original owner is unknown.