Does shunning a Christian friend invalidate an oath, such that no expiation is required to resume contact with him, by analogy with shunning a Muslim?

Islam has clarified the regulations governing a Muslim's relationship with others. Whoever swears an oath and then sees that something else is better than it, must expiate for his oath and do that which is better, according to the saying of the Prophet, peace and blessings be upon him: "Whoever swears an oath and then sees something else better than it, let him do that which is better and expiate for his oath." The expiation for an oath is: feeding ten poor persons, or clothing them, or freeing a slave; and if he cannot find any of these, then fasting for three days. Accordingly, if a Muslim wishes to resume interaction with a Christian, he must expiate for his oath. This interaction must be in accordance with Sharia regulations. The summary is that whoever swore an oath to boycott a Christian or anyone else, and then wished to resume interaction with them, must expiate for his oath, even if the boycott was unlawful.