Is taking a loan for two days for the purpose of proving possession of money without spending it, then returning it, considered usury (riba), and can this be avoided by an agreement not to spend it or by other means?

If you wish to borrow an amount on the condition of paying an increase to the lender, this is forbidden and constitutes usury (riba). Ibn Abd al-Barr said: "Every increase in a loan, or benefit enjoyed by the lender, is usury, even if it were a handful of fodder. And that is forbidden if it is stipulated as a condition." There is a consensus that stipulating an increase or a gift in a loan is usury, due to the prohibition of every loan that brings a benefit to the lender. The way to avoid usury is to seek a loan that does not stipulate an increase.