Fill a large pot with water and bring it to a boil.
Add the baking soda, hydrogen peroxide, and dish soap to the water. Stir gently.
Submerge your white towels and reduce the heat to a gentle boil. Let them simmer for 30–45 minutes.
Carefully remove the towels using tongs and rinse thoroughly with cool water.
Wring out the towels and hang to dry in a sunny spot if possible—sunlight naturally brightens whites.