Allah ﷻ said: "Verily, the believers are brothers" [Hujurat: 10].
And Allah ﷻ said, reporting about Noah ﷺ: "And I advise you sincerely" [Araf: 62].
And about Hud ﷺ: "And I am to you a trustworthy advisor" [Araf: 68].
And as for the ahadith:
قَالَ تَعَالَى: ﴿إِنَّمَا المُؤْمِنُونَ إخْوَةٌ﴾ [الحجرات: ١٠]،
وَقالَ تَعَالَى: إخبارًا عن نوحٍ ﷺ: ﴿وَأنْصَحُ لَكُمْ﴾ [الأعراف: ٦٢]،
وعن هود ﷺ: ﴿وَأنَا لَكُمْ نَاصِحٌ أمِينٌ﴾ [الأعراف: ٦٨].
وأما الأحاديث:
that the Prophet ﷺ said: "The religion is sincerity." We said, "To whom?" He said "To Allah, to His Book, To His Messenger, and to the leaders of the Muslims and their masses."
أَنَّ النَّبِيَّ ﷺ قَالَ: «الدِّينُ النَّصِيحَةُ۔» قُلْنَا: لِمَنْ؟ قَالَ: «لِلَّهِ، وَلِكِتَابِهِ، وَلِرَسُولِهِ، وَلأَئِمَّةِ الْمُسْلِمِينَ وَعَامَّتِهِمْ۔»
I gave the pledge of allegiance to Messenger of Allah ﷺ for to offer prayers perfectly, to pay Zakat regularly, and to give good advice to every Muslim.
بَايَعْتُ رَسُولَ اللَّهِ ﷺ عَلَى إِقَامِ الصَّلاَةِ وَإِيتَاءِ الزَّكَاةِ وَالنُّصْحِ لِكُلِّ مُسْلِمٍ
The Prophet ﷺ said, "None of you will have faith till he loves for his ˹believing˺ brother what he loves for himself."
عَنِ النَّبِيِّ ﷺ قَالَ: «لا يُؤْمِنُ أَحَدُكُمْ حَتَّى يُحِبَّ لأَخِيهِ مَا يُحِبُّ لِنَفْسِهِ»۔