Please inform of the correct definition of Nikah-e-Muyasar and its ruling as per Shari'ah with full evidence.
Nikah-e-Muyassar is when a man marries a woman for period of time. The ruling on such marriages is that if the marriage was contracted to last for a specific period of time, then this is called Nikah-e-Muwaqat. This, being a type of Mut'a, is unlawful as per Shari'ah, and must be avoided. If during the marriage contract no specific period was mentioned, but one party intends uphold the marriage temporarily and end it after some time by means of divorce, then such Nikah is valid according to the Jurist, however, since this is contrary to the objective of marriage, it is disliked to marry with such intentions. For this reason, this should be avoid as much as possible.
And Allah knows best.
کما فی الدر المختار: (وبطل نکاح متعۃ وموقت) وإن جہلت المدۃ أو طالت فی الأصح ولیس منہ مالو نکحہا علی أن یطلقہا بعد شہر أو نوی مکثہ معہا مدۃ معینۃ۔ الخ (ج۳، ص۵۱)۔
وفی فتح القدیر: أمّا لو تزوج وفی نیتہ أن یطلقہا بعد مدّۃ نواہا صح۔ الخ (ج۳، ص۱۵۲) واللہ اعلم