Imam Muhammad b. Ali Baqir (a.s.) informed: A man came to the Messenger of Allah (s.a.w.a.) and asked – If one testifies that there is no god but Allah, is he considered a believer?
The Messenger of Allah (s.a.w.a.) replied – Our enemies will join the Jews and the Christians (on the Day of Judgement). No one can enter Paradise without loving me, and those who think they love me but hate Ali b. Abi Talib are liars. Al-Amaali p 222
(One of the possible meanings that can be derived from this valuable report is that those who testify that there is no god but Allah but do not complete it with the second and third statement of the testimony are the enemies to whom the Prophet (s.a.w.a.))