Why only 3 Matzot?
The usual explanation of the four cups of wine is that there are four promises of salvation in Ex. 6, each cup being a toast to the fulfilment of one of the promises.
There is a fifth promise, “I will bring you in (to the Promised Land)”, which has only partly been fulfilled, so some say that a fifth cup should be placed on the table but not (yet) drunk.
Yet matzah is the chief food at the seder, so why not have four matzot for the four promises?
Matzah would be inappropriate because it is the bread of affliction; the three matzot are for other reasons.
To toast the fulfilment of promises of redemption we need something which symbolises joy, and that, according to Psalm 104:15, is wine: “Wine rejoices the heart of man”.
