Oneness, Uniqueness of Allah (Tawheed)
حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا سُفْيَانُ، عَنْ صَالِحٍ، عَنْ عُبَيْدِ اللَّهِ، عَنْ زَيْدِ بْنِ خَالِدٍ، قَالَ مُطِرَ النَّبِيُّ صلى الله عليه وسلم فَقَالَ " قَالَ اللَّهُ أَصْبَحَ مِنْ عِبَادِي كَافِرٌ بِي وَمُؤْمِنٌ بِي ".Narrated Zaid bin Khalid:It rained (because of the Prophet's invocation for rain) and the Prophet (ﷺ) said, "Allah said, 'Some of My slaves have become disbelievers in Me, and some others, believers in Me
From Sahih al-Bukhari, whose reports the scholars accept as authentic.