Why killing Human beings a sin but not killing animals?
Peace be onto you, Killing animals without any purpose (eating or attacking you (Lion, Tiger) etc) is ofcourse a sin. Animals are innocent and there should be a purpose for every doing. If you are killing them without a reason so ofcourse it’s bad because God says in the Qur’an “There is not an animal (that lives) on the earth, nor a being that flies on its wings, but (forms part of) communities like you. Nothing have we omitted from the Book, and they (all) shall be gathered to their Lord in the end” [Qur’an 6:38] Prophet Muhammad (PBUH) is also reported to have said: “There is no man who kills [even] a sparrow or anything smaller, without its deserving it, but God will question him about it [on the judgment day],” and “Whoever is kind to the creatures of God is kind to himself.” Thanks, Hope I answered!