פירוש על שבת 43:7

The reason for Rav: [He prohibits it] from one lamp to [another] lamp, due to contempt for the commandment. For he lights a wood chip that is not part of the commandment from a lamp of the commandment and lights the rest from it.

He weakens it: As it appears like one who is taking light and drawing away some of the vitality of its oil.

From lamp to lamp: He brings one lamp next to the [other] lamp, and they are both of the commandment; and [he does] not [do it] with a wood chip.