The first (of) Obligations upon the servant – Shaykh al-Uthaymeen
Shaykh al-Uthaymeen (may Allah have mercy upon him) mentioned:
“The first of obligations upon the creation, is the first of what they are invited to. The prophet ﷺ clarified this to Muaadh bin Jabal when he sent him to Yemen and he said:
“إنك تأتي قوما أهل كتاب، فليكن أول ما تدعوهم إليه شهادة أن لا إله إلا الله وأن محمدا رسول الله”
“Indeed you are going to a people from ahlu kitab (jews and christians), so let the first thing that you call them to is that none has the right to be worshiped except Allah and that Muhammad is the messenger of Allah”
So this is the first of the obligations upon the servants; that they worship Allah and they bear witness that His messenger (Muhammad) was sent with the message (of Islam) and they must actualize sincerity (worshiping Allah alone) and following (His messenger) as these two are conditions for the acceptance of all acts of worship. Therefore this is the first thing which is obligated upon the servants…”
Fiqh al-Ibaadaat pg. 14
Translated by Abu Anas Atif Hasan