מנא לן - מנא הני מילי

Sometimes the gemara asks "mina lan?" and sometimes "mina hani mili?" - both essentially mean the same thing. "What is the source for this ruling?".

However there is a difference. The mishna in kiddushin [26a] says that a field be bought with kesef, shtar or chazaka. The mishna continues and teaches that you can purchase movable items with meshicha. The mishna concludes that one may purchase movable items by making a kinyan on land [kinyan agav].

Now it gets fascinating. When inquiring about the ability to buy with kesef, shtar, chazaka and meshicha the gemara asks "mina lan". When inquiring about kinyan agav the gemara asks "mina hani mili?". Why the change?

Rav Yaakov Chaim Sofer Shlita [Kerem Yaakov simman yud] explains that "mina lan" means that we agree that it's true and are just wondering what the source is. "Mina hani mili" means that we are questioning the very premise that your halacha is true and are therefore asking "Where do you get that from?"

Now it's beautiful. Kesef, shtar, chazaka and meshicha we have a precedent for in other halachos. Kesef and shtar are koneh an isha, chazaka and meshicha are koneh an eved kinaani. So the gemara asks "Mina lan"? It's true but what's the source. However we have no precedent for kinyan agav, so the gemara asks, "Hold on, mina hani mili?" How do you know that it true at all that there is such a thing as a kinyan agav. What is your source?

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