A person says 'I sell you whatever my field will produce.' Does the buyer acquire anything?
One cannot transfer something that hasn't come into existence. Future produce is not yet in the world, so the sale is void — the buyer acquires nothing.
Question 2
A poor fisherman says 'What my net brings up from the sea today is sold to you.' Is this sale valid?
The Rabbis created an exception for a starving fisherman pledging today's catch. The word 'today' and the extreme need make this valid as an exception to preserve his livelihood.
Question 3
Can a person transfer ownership of 'the fragrance of this apple' to a colleague?
An object must have physical substance (mamash) to be transferred. Fragrance, taste, and color have no substance and cannot be subjects of sale or gift. One must transfer the physical apple itself.
Question 4
A seller quotes the market price for wheat he doesn't own and the buyer says 'I am relying on you.' The seller then retracts. What is the consequence?
When a seller commits to market price and the buyer explicitly relies on him, the seller is obligated to fulfill the sale. If he retracts, he receives the mi shepara adjuration.
Question 5
A person on his deathbed says 'Whatever this tree produces should go to the poor.' Does this take effect?
The Rambam rules that pledges to the poor (tzedakah) are governed by vow law, not commerce law. The Torah obligates one to fulfill vows even regarding future items: 'He shall act according to what he utters.'