O You who have chosen to be graced with belief! Ask not unnecessary details of the things as the Israelites did to Moses about the cow. This attitude may bring unpleasant consequences for you. But if you ask them as the Qur'an is being revealed, the minor details of Ordinances might be given which will be hard for you to follow. The general rule has been given that all pure and good things are Permissible to you. Your questions are very clearly answered in the Qur'an (5:15), (15:1), (22:40). Allah has absolved you in this respect for Allah is Forgiving, Clement. (The Qur'an is for all times, and while the basic Laws and Principles remain immutable, minor details are intended to be flexible according to temporal and spatial requirements (11:1). "This day I have perfected your DEEN for you, completed My favor upon you, and chosen for you Islam as the System of Life" (5:3)).