Should a mother wish to redeem her firstborn son whose father is not in the city she may redeem him; she may do so herself or have someone, as the father's messenger, do so. Just as HaSHa"CH (Rabbi Shabetai Hacohen) and the T"Z (Rabbi David HaLevy Segal, author of the Torei Zahav) wrote in Yorei De'ah Section 305 in the name of several rabbis, differing from Rabbeinu Mosheh Isserlich. We have also done so; I God's servant, in lieu of the boy's father, recited the blessing "who sanctified us with His commandments and commanded us to redeem the firstborn". As Maran wrote, concerning one who redeems himself.