As the record date is 7th August, you need to hold stocks on the 7th August closing. You need not hold it till 2nd Sept. The list as taken on 7th August would be processed and instructions given to Bank and the dividends credited by 1st Sept.
Edit: To Clarify Victor's comment
Typically from the time one sells the stocks to the time it actually gets transferred has a clearing cycle. Most stock exchanges have 2 or 3 days cycles. i.e. if I sell the stock today, it is still in my name. The money is still with the buyer. On Day 1, the positions are arrived at. On Day 2 the stock gets credited to the buyer and the funds gets credit to seller.
As the question was specific whether to hold the stock till 7th or 22nd Sept, my initial answer was simple. The illustration by Victor is more accurate.