The Foundation Stone Haggadah: Urchatz 2
Teshuva is referred to metaphorically in Tanach as washing.
There are two washings in the Seder, Urchatz and Rachtza the first without a Beracha, the second, with a Beracha. He explains that there is a concept of Teshuva on Teshuva; The first Teshuva is on the “big” sins. The second is a more detailed Teshuva that addresses the finer details. When a person realizes that the first Teshuva was incomplete and that it has to be refined, he is doing Teshuva on his Teshuva. It is only the second Teshuva that can be accompanied by a Beracha.