We have an obligation (Saint Gregory the Theologian)

The law (Deut. 22, 1-4) commands that if an animal [belonging to someone else] strays or falls into a ditch, we should rescue it and take care of it. Given that people are not of any less value, it follows that we should show great kindness towards other human beings, since we have a duty to be sympathetic even to irrational beasts.