Where can I find historical data for WTI Price, gold price, CRB index for my research work?
Is there any website from where I can download these data?
Although I think your question will be flagged for "basic knowledge" you can find free sources for this data including Yahoo Finance, Quandl. Commercial data vendors also provide this information.
However, you really need to define what sort of data you are trying to find. Spot prices (for physical delivery), spot prices (for cash settled) or futures data (for future physical delivery) or something else.
For example, "gold price" could be the cash-settled FX contract, LBMA "ring" settlements, Gold futures traded on CME/NYMEX, physical gold traded through venues like Perth Mint etc.
Full disclosure: Norgate/Premium Data offers commodities and futures data.