EXOD547 R. Akiva expounded: "from My altar" [i.e., from near My altar], and not "from upon My altar" i.e., A priest who is upon the altar (i.e., in the midst of sacrificing) is not to be taken thence to be killed for a murder that he has committed]. And this applies only to an instance where he is to be killed; but where one is to be saved [i.e., if this priest can testify to save someone's life], then even "from upon My altar." From here it is derived [by a fortiori reasoning] that the saving of life overrides the Sabbath (Yoma 5:1)