All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The leading scholars (Imams) have two different opinions regarding Maghrib prayer time:
According to the first opinion, Maghrib prayer time starts just after sunset, i.e., when the sun sinks below the horizon. Its time ends quickly leaving just enough time for the Muslim to call the Aathaan, to perform ablution, to put on his clothes, to call the Iqama (call for the establishment of the prayer), and to perform five Rak’ahs.
The second opinion concurs with the first one in the starting time. But for these scholars, the finishing time is after the disappearance of the twilight, the red glow of sunset from the sky.
This means that Maghrib here is about three times longer than the one above (i.e. according to the first opinion).
The second opinion is the one followed by most Muslims. Its evidence is the Hadeeth narrated by Muslim, which reads: “The Maghrib prayer time is due as long as the twilight hasn't disappeared.” As for the disliked time, it is detestable to delay Maghrib prayer to its last time without a genuine reason.
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Allah knows best.