The Prophet (ﷺ) said, "O Mu`adh! Do you know what Allah's Right upon His slaves is?" I said, "Allah and His Apostle know best." The Prophet (ﷺ) said, "To worship Him (Allah) Alone and to join none in worship with Him (Allah). Do you know what their right upon Him is?" I replied, "Allah and His Apostle know best." The Prophet (ﷺ) said, "Not to punish them (if they do so).
Sahih al-Bukhari Book 97, Hadith 3
← Previous Hadith When the Prophet (ﷺ) sent Mu`adh to Yemen, he said to him, "You are going to a nation from the people of the Scripture, so let the first thing to which you will invite them, be the Tauhid of Allah. If they learn that, tell them that Allah has enjoined on them, five prayers to be offered in one day and one night. And if they pray, tell them that Allah has enjoined on them Zakat of their properties and it is to be taken from the rich among them and given to the poor. And if they agree to that, then take from them Zakat but avoid the best property of the people."

Sahih al-Bukhari Book 97, Hadith 2 Next Hadith → A man heard another man reciting (in the prayers): 'Say (O Muhammad): "He is Allah, the One." (112.1) And he recited it repeatedly. When it was morning, he went to the Prophet (ﷺ) and informed him about that as if he considered that the recitation of that Sura by itself was not enough. Allah's Messenger (ﷺ) said, "By Him in Whose Hand my life is, it is equal to one-third of the Qur'an."

Sahih al-Bukhari Book 97, Hadith 4