When do the optional and necessary times for prayers begin and end, and is it permissible to pray only during the necessary time when there is an excuse? What are the excuses that permit this? How long is the optional time for the Asr prayer? And does the optional Dhuhr time extend for four rak'ahs after the Asr time begins?

Firstly: Scholars differ on whether there is a time of necessity (waqt darurah) for the five daily prayers. The Hanbalis believe there is a time of necessity for Asr (from the yellowing of the sun until sunset) and Isha (from one-third of the night until the second dawn), but not for Fajr, Dhuhr, and Maghrib. The Malikis, on the other hand, believe there is a time of necessity for all five prayers.

Secondly: It is not permissible to delay a prayer until the time of necessity without an excuse. Among the valid excuses for this are: disbelief (if one embraces Islam), childhood (if one reaches puberty), unconsciousness, insanity, sleep, forgetfulness, and menstruation and post-natal bleeding (if one becomes pure). Whoever performs the prayer during the time of necessity due to these excuses does not incur sin.

Thirdly: The time of necessity for the Asr prayer begins from the yellowing of the sun and ends at sunset. The optional time (waqt ikhtiyari) for Asr extends from the end of Dhuhr's time until the yellowing of the sun. It cannot be estimated as half or otherwise because it varies depending on time and place.

Fourthly: The statement by some jurists that the optional time for Dhuhr extends by the duration of four rak'ahs after the entry of Asr's time is a point of contention among the Malikis. The origin of this dispute lies in the interpretation of the Hadith of Jibril (peace be upon him) regarding prayer times, and whether "he prayed with me" (صلى بي) means "he legislated" or "he finished."

Fifthly: Some scholars permit combining two prayers while resident for a need, not as a habit, based on the action of the Prophet (peace be upon him) in the Hadith of Ibn Abbas, where he prayed Dhuhr and Asr together in Medina without fear or travel, to facilitate matters for his Ummah.