We are forbidden to kill or to cause pain to any living creature unless it is necessary.
As Ramak (R’ Moshe Cordovero) says in Tomer Devorah (ch. 3), one “should be a father to all the creatures of the Holy One, Blessed is He,” and one’s “mercy should extend to all creatures, neither destroying nor despising any of them. …In this way man’s pity should be extended to all the works of the Blessed One just as the Supernal Wisdom despises no created thing for they are all created from that source.” One “should despise no created thing, for they all were created in Wisdom. He should not uproot anything which grows, unless it is necessary, nor kill any living thing unless it is necessary.”