Class Sixty One in Section Six of The first idea

רס”ו ע’ תר”ס-ס”א. In קליפה there is conflict: too much אור would destroy. But in קדושה there is no conflict: a lower כלי in a higher world becomes the higher world. In other words: כלים that are אלקות when included in higher levels aren’t destroyed, because they are כלים for the אור, therefore they can carry from those highest of levels. The Neshama does this to become a מהלך.