Distinguish two moments:
Before acceptance: ending the session causes the outstanding offer to lapse; no sale has been formed.
After acceptance: departure alone does not cancel an already binding sale.
The governing question is whether acceptance had occurred before the session ended.
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Kitab al-Buyu: Offer, Acceptance, Binding Sales and Price Clarity
Distinguish two moments:
Before acceptance: ending the session causes the outstanding offer to lapse; no sale has been formed.
After acceptance: departure alone does not cancel an already binding sale.
The governing question is whether acceptance had occurred before the session ended.