Issues in al-Rawd (1):

He says: “There is no riba between a master and his slave.” Thus, a person may buy three dirhams for two dirhams from his slave, because the property belongs to him, as the Prophet (peace and blessings be upon him) said: “Whoever sells a slave who owns property, then his property belongs to the one who sold him.” (2)

Does riba apply between a father and his son?

The answer is yes: it applies between a father and his son, because the son’s property is independent and the father’s property is independent. The fact that a father may appropriate for himself whatever he wishes from his child’s property does not mean that his child’s property belongs to him. As for the Prophet’s statement (peace and blessings be upon him), “You and your property belong to your father,” (3) its meaning is that your father may take ownership of some of your property; it does not mean that you belong to your father, or that your property belongs to him. Scholarly consensus precludes this, for the son is not the property of his father; and if the son is not his father’s property, then his wealth is not his father’s property. This is why Allah the Exalted says:

“Allah instructs you concerning your children: for the male, what is equal to the share of two females.” [al-Nisa’ 4:11]

Thus, He made inheritance take place between fathers and children; had children belonged to their fathers, inheritance would not take place.

Does riba apply between a husband and his wife?

The answer is yes: it applies.

Issue: Two sisters may sometimes purchase jewelry, and when they arrive home, one of them says, “I do not want this jewelry.” The other says, “I want it.” So the first says, “Let us exchange,” despite there being a disparity between them; that is, this one’s bracelet is wide