What is the ruling on praying Friday prayer in the mosque for someone who swore by divorce fifty times that he would not pray in the mosque during the month of Ramadan, and does the oath take effect if he prays in the mosque?

Hastiness in uttering words of divorce is dangerous and has negative consequences. It is something whose serious and jesting utterances are both binding, due to the Prophet's (peace be upon him) saying: "There are three things whose serious utterance is binding and whose jesting utterance is binding: marriage, divorce, and رجعة (return to the marriage)."