What is the definition of speculation (mudarabah) and what is its ruling, and is it permissible for the speculator (mudarib) to take a guarantee from the counterparty, such as a promissory note?

Ibn Qudamah said: "Mudarabah is when a man gives his money to another to trade with it, on the condition that any profit gained will be shared between them according to their agreement." As for Al-Jurjani, he said: "It is a contract of partnership in profit, with money from one person and work from another. It is first a deposit, then an agency when it is worked with, a partnership if there is profit, usurpation if he violates (the terms), a commodity if all the profit is stipulated for the owner, and a loan if it is stipulated for the Mudarib." It is permissible to take a document to authenticate the worker's receipt of the money, based on the verse: {O you who have believed, when you contract a debt for a specified term, write it down}. However, if what is meant by "guarantee note" is that the Mudarib guarantees the principal capital in case of loss, then this is not permissible, and the Mudarabah would then be invalid.