פירוש על קידושין 34:9

The author of the baraita also learns the halakhah that the son takes his father’s place in redeeming the ancestral field from the argument against yibum—is there yibum when there is a son? Thus we can see that we need that argument to refute the counterargument that a brother, or another heir, can inherit the slave. Only a son inherits the slave....