Firstly, I'd like to note that any food product — with the exception of fresh and unprocessed fruit and vegetables — must have reliable kosher for Passover certification in order to be eaten on Passover. Even if the food item itself contains no chametz, it could contain minute amounts of chametz ingredients, and/or it could have been processed with utensils or machinery which may contain traces of chametz.

That said, hummus, which is made from chickpeas, cannot be eaten on Passover by Ashkenazi Jews. For approximately the last thousand years, Jews of Ashkenazi descent have observed the prohibition of eating kitniyot, legumes, on Passover. Kitniyot includes legumes such as beans, peas, corn, rice, chickpeas, sesame, etc. The rationale behind this prohibition is the possibility of producing kitniyot-based flour and bread, which resembles wheat flour and wheat bread. Permitting the consumption of rice flour bread, for example, would create the likelihood for confusion and error on Passover.

Different Sephardic communities have various customs with regards to kitniyot. However, even if you do eat chickpeas on Passover, be sure that the hummus has kosher for Passover certification.

Best wishes,

Chani Benjaminson
Chabad.org