Is stipulating the option until sunrise or sunset valid?
Chapter on the Option of the Two Parties in Sale
Al-Mughni
Book of Sales
Primary text
Stipulating the option until sunrise or sunset is valid. Sunrise is defined as the appearance of the sun over the horizon, just as sunset is the sinking of the disc. If cloud cover prevents immediate knowledge of sunrise or sunset, the option remains in effect until certainty of the event is established, similar to conditional divorce depending on the same event.
Supporting text
Some scholars deem stipulation until sunrise invalid because clouds might obscure the exact time of its rising, making the timing uncertain. Furthermore, setting the option until sunrise from under the clouds or until its setting under the clouds renders the option unknown and thus invalid according to the soundest position in the madhhab.