Iman includes believing in Allah and His Messenger and having faith in what Allah and His Messenger informed of and in Allah's Commandments and Prohibitions.

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The faith is not complete unless they obey Him and His Messenger in all affairs. Committing sins weakens faith, so the believers obey Allah (Exalted be He) and His Messenger (peace be upon him) in all affairs and avoid all sins.

Source: The Essence of `Ibadah and Tawhid of the Creator , Volume 5 – Fatwas of  ibn baz, https://www.alifta.gov.sa