The Torah said, “Whatever touches the Altar shall be sanctified.” This means that if some sacrificial parts were put on the Altar, they may not be taken down, even if they should not be put there in the first place. Basically this applies when the sacrifice was valid when it entered the Courtyard, and the disqualification occurred later, as part of the service.
Earlier we learned that if one slaughtered an offering, such as a burned offering, which must be slaughtered to the North of the Altar, in the South, he invalidated it, and that misappropriation still applies in this case. A related questions was asked: if they put limbs of this invalid offering on the Altar, must they keep them there? If we say that an offering slaughtered at night has to be kept on the Altar, then perhaps one slaughtered in the South of the Courtyard is the same way, and it too has to stay on the Altar. Or perhaps on offering slaughtered in the South is worse, and it is as if choked, not slaughtered at all? Rav Yosef and Rabbah argued this matter out, and Rav Yosef found an incontrovertible proof that once it went up on the Altar, it does not go down.
Art: J. Duvall - Sheep And Lambs On A Hillside