And he said unto them, What man shall there be among you, that shall have one sheep, and if it fall into a pit on the sabbath day, will he not lay hold on it, and lift it out? If it fall into a pit on the Sabbath - day, etc. - It was a canon among the Jews: "We must take a tender care of the goods of an Israelite." Hence: -
"If a beast fall into a ditch, or into a pool of water, let (the owner) bring him food in that place if he can; but, if he cannot, let him bring clothes and litter, and bear up the beast; whence, if he can come up, let him come up, etc."
"If a beast or its foal fall into a ditch on a holy day, R. Lazar saith, Let him lift up the former to kill him, and let him kill him; but let him give fodder to the other, lest he die in that place. R. Joshua saith, Let him lift up the former with the intention of killing him, although he kill him not; let him lift up the other also, although it be not in his mind to kill him." To these canons our Lord seems here very properly to appeal, in vindication of his intention to heal the distressed man. See Lightfoot.
Self-interest is a very decisive casuist, and removes abundance of scruples in a moment. It is always the first consulted, and the must readily obeyed. It is not sinful to hearken to it, but it must not govern nor determine by itself.