Is my friend obligated to pay $126,0 after the share price dropped, given that he took my shares to sell them and buy other shares, promising to return them, then procrastinated in returning them, and their price rose, then fell?

For stock trading, it is a condition that the stocks must be pure, meaning shares of companies with permissible activities that do not deal in usury. It is permissible to lend anything that can be sold, with the exception of human beings. However, there is a difference of opinion regarding lending stocks. Stock prices fluctuate, and it is difficult to achieve equivalence in them, which may lead to disputes. Some scholars consider lending stocks impermissible, while others permit it by considering their value on the day of the loan, and this is the most equitable opinion. So, if you lend stocks to your friend, he must return their value to you on the day of the loan, unless you accept the stocks themselves.