Marbeh Lisaper on Pesach Haggadah
Kadesh 1 קדש א׳

Kadesh u’Rechatz: A person should first sanctify himself so that he can turn away from sin, and afterwards one should perform mitzvot, as scripture states, “Turn away from evil and do good.” Therefore we say, Kadesh u’Rechatz: Sanctify yourself by leaving transgression and afterwards cleanse yourself so that you will not be like the person who immerses himself in the Mikvah while holding on to an impure creature. Nothing should stand between you and purity.