If a [non-Jewish] slave, a woman, or a minor recited [Hallel] for someone, he must repeat after them whatever they say —- and let it be a curse upon him!  If an adult was reciting for him, he must respond after him, “Hallelu Yah.”

In a place where they are accustomed to repeat, he repeats; [where the custom is] to recite as is, he recites as is; [where the custom is] to recite a blessing after it, he recites a blessing after it —- everything [must be done] in accord with the local custom.  If one purchases a lulav from his friend during Shemittah, he must give him the esrog as a gift, because it is forbidden to purchase it during Shemittah.