Earlier I wrote about the Unification of God in Islam. View Post. This post is just going to be a slight explanation about that. Out of all things in Islam, this is the most important. All the good actions, that can be done, this is the only action that is required to be done by a Muslim, 24 hours a day, 7 days a week, 365 days out of the year(366 during a leap year.) The prayers Muslims do, is only 5 times a day. But a Muslim must be in the state of Tawhid, at all states. Meaning, a Muslim must believe that there is only one God, at all times. Allah says in the Qur’an: 
“Verily, Allâh forgives not that partners should be set up with Him In worship, but He forgives except that (anything else) to whom He pleases, and whoever sets up partners with Allâh In worship, He has indeed invented a tremendous sin.”
Meaning in Islam, all sins are forgiven except associating partners with Allah(shirk). This is why the Unity(tawheed) of god is the most important part of Islam.
Come Learn About Islam 