Times When Prayer Is Prohibited

Question:
I hope you will guide us to a method or a book for determining or obligating that regarding prayer using rational measures.

Answer:
It is clear that no book is needed. The prohibition of prayer from the 'Asr prayer until the setting of the sun is one instance. The second is from the Fajr prayer until the sun has risen the height of a spear; this is something that can be observed. When you see the sun has risen above the eastern horizon by the length of a spear, prayer is permissible. The third is when the sun is in the middle of the sky, directly overhead, until it moves toward the west, even if only slightly. When the shadow appears from the east, prayer is permissible. As long as there is no shadow and the sun is directly overhead, this is a short time; they say it does not allow for prayer, it does not allow for prayer, yes. However, when the sun reaches this point and is directly overhead, refrain from prayer until it moves toward the west. The sign of its movement is the appearance of the shadow toward the east. These are the times when prayer is prohibited.