"and his name will not be wiped out in Israel": to exclude (from yibum) the wife of one who is impotent, whose name is already "wiped out."
(Ibid. 7) "And if the man shall not desire to take his yevamah": and not "if the L-rd shall not desire her.": (From this) I would exclude (from chalitzah [yibum release]) those arayoth which are liable to judicial death penalties, but I would not exclude those which are liable (only) to kareth; it is, therefore, written "He does not desire to have me in yibum," and not "the L-rd does not desire her."