I heard about a thing called Profit Purification. I learned that when a Shariah-compliant company pays dividends, there is a small percentage of non-compliant profit which we have to pay out (as charity) to purify the profit we earn. But I have a question, if someone can answer it: When we buy the stock of that Shariah-compliant company at a low price and sell it at a higher price, should we have to pay out the purification money?