What is the ruling on falsely accusing one's wife of adultery and defaming her without just cause, then justifying a request for divorce on that basis, especially when there are two children involved, and what is the fatwa if one is asked to testify and swear an oath concerning this falsehood?

Falsely accusing a Muslim woman of zina (fornication/adultery) is unlawful and a grave sin. Allah says: "And those who accuse chaste women and then do not produce four witnesses - flog them eighty lashes and never accept from them any testimony ever, and those are the defiantly disobedient." Falsely accusing one's wife of meeting another man is a forbidden slander. The Prophet, peace and blessings be upon him, said: "Whoever says about a believer something that is not true, Allah will make him dwell in the mire of corruption until he retracts what he said, and he will not be able to retract it." If one swears an oath to this false accusation, he has committed a false oath (al-yameen al-ghamūs), which is one of the major sins, about which the Prophet, peace and blessings be upon him, said: "A false oath leaves homes desolate."