Many folks who’ve been rooting or modding their device, sooner or later wants return to defaults/stock software, possibly they just realized that their smartphones has better performance when running an original firmware from Samsung, if you agree with that then you’ll need to download a stock firmware for Galaxy S4. By using the original shipped firmware from Samsung and with the help of Odin you can restore your smartphone to original condition, same as when you purchase it from the store.
As you know, the new Galaxy S4 has been officially released in April and it’s available in almost every country right now. Like the previous Galaxy devices, these smartphone is the most-awaited Android smartphone this year, and were able to divert the world attention that were previously focused on HTC One and Sony Xperia Z, although in terms of design and physical appearance are not much has changed, the progress has mostly to new features including Smart Scroll, Smart Gestures, etc.
Each Samsung Galaxy S4 original firmware is different for each phone model, so in case you have a carrier-branded device you should download the appropriate file for your phone model number, this can be found in Settings -> More tab -> About device.
Almost all phone models have a stock Android 4.2.2 (Jelly Bean) firmware, such as the SGH-I337 (AT&T), U.S. T-Mobile (SGH-M919), Sprint (SPH-L720), Verizon (SCH-I545), CA Bell/Rogers/SaskTel, EU Vodafone/Orange/O2 (GT-I9505) and a lot more, but not all of them are available at the same time.
When you aren’t able to find a specific file for your smartphone, you have to wait, since a stock firmware will likely be available after an official OTA update has been rolled out.