Answer: 1. Islam, as the prayer of a disbeliever is invalid
2. Sanity, as the prayer of an insane person is invalid
3. Discernment, as the prayer of the undiscerning child is invalid
4. The intention
5. Commencement of the prescribed time
6. Tahārah, i.e., removal of Hadath (ritual impurity)
7. Purification from physical impurity
8. Covering the ‘Awrah (parts of the body that must be covered)
9. Facing the Qiblah (direction of the Ka‘bah)