737. If a stick, a pole, or anything similar to it, which acts as an indicator (shakhis) is made to stand on a level ground, its shadow will fall westwards when the sun rises in the morning, and as the sun continues to rise the shadow cast by the indicator will reduce in size. And in our cities it becomes smallest at the time of the commencement of Zuhr.
And as Zuhr passes the shadow cast by the indicator turns eastwards, and as the sun moves towards west the shadow gets longer. Based on this, when the shadow is the shortest, and it begins getting longer again, it is known that Zuhr has taken place. However, in other cities like in Mecca, the shadow disappears totally, so, when it reappears it indicates Zuhr.
739. Zuhr and Asr Namaz have each especial and common times. The special time for Zuhr prayer is from the beginning of Zuhr until the time required for such prayer.and if one offers the whole of Asr prayers in this time his prayers is void. And the special time for Asr prayer is the time required for such prayer before Maghrib, and if a person has not offered his Zuhr prayer until this time, his Zuhr Namaz is Qadha and he should offer Asr prayer. And between the special time of Zuhr Namaz and special time of Asr Namaz, is the common time of Zuhr and Asr Namaz and if a person offers unintentionally the whole of Asr prayers in this time before Zuhr prayer it is valid and is considered as Asr. And then he should offer Zuhr prayers . But It is not befitting that he abandons the precaution by offering 4 Rak'ats with the intention of relieving oneself of responsibility.
740. If a person begins offering Asr prayers forgetfully before Zuhr prayers and during the prayers he realises that he has committed a mistake,if it is in common time, he should revert his Niyyat to Zuhr prayers i.e. he should intend that from now onwards till the end of the prayers, it would be Zuhr prayers. After completing the prayers, he will offer Asr prayers. And if it is in the special time for Zuhr his pray is volid , he realises during the prayers or after that.
742. The time of Friday prayer starts with the decline of the sun (midday) and it continues as long as it take time.