Interpretation of the Hadeeth “Let the first thing you call them to.”

Shaykh al-Fawzan (may Allah preserve him) said :

“ When the Messenger (peace and blessings of Allah be upon him) sent Mu’az to Yemen, he drew for him the methodology (path) of the call, saying to him: “Verily, you will come to the people of the Book, let the first thing you call them to be evidence that there is no other deity worthy of worship except Allah .

Pay attention, the Prophet (peace and blessings of Allah be upon him) began with Tawheed! “If they submit to you in this” – that is, they testify that there is no other deity worthy of worship except Allah and the correct belief will be established –

“ Then let them know that Allah has obligated them to perform five prayers daily. If they submit to you in this, then let them know that Allah has obligated their rich to make donations to the poor ”
al-Bukhari, 1395 and Muslim, 19.

? (See “Ahammiyat at-Tawhid” Sheikh Fawzan, p. 9)