Wait two months and when he wants food he will let you know. Breastfed babies do not require food until they are a year old. As a general rule a baby should not get any food items until they have teeth. The teeth are the sign that the digestive system is ready.
Meantime if he wants to chew get Zwieback or something he can hold in his hand and gum. Ritz crackers have lots of fat in them so you really want something purer for his developing digestion.
My parents gave us Zweiback and I gave it to my children.
I took this out of Wikipedia to explain Zweiback's ingredients and popularity to you.
Zwieback is a type of crisp, sweetened bread, made with eggs and baked twice.
It is sliced before it is baked a second time, which produces crisp, brittle slices that closely resemble melba toast.[1] Zwieback is commonly used to feed teething children[1], and as the first solid food for patients with an upset stomach.
The name comes from German zwei ("two") or zwie ("twi-"), and backen, meaning "to bake".[2] Zwieback hence literally translates to "twice-baked".
Zwieback originated in East Prussia, Germany. The Mennonites brought Zwieback to Russia (now Ukraine); during and after the Russian Revolution, they brought Zwieback to Canada, and other parts of the world.