The Prophet said to 'Ali: "Would it not please you to be to me as Harun was to Musa?" (Using translation from Ibn Mājah 115)   

أَنَّ رَسُولَ اللهِ ﷺ قَالَ لِعَلِيٍّ «أَلَا تَرْضَى أَنْ تَكُونَ مِنِّي بِمَنْزِلَةِ هَارُونَ مِنْ مُوسَى؟»  

from the Prophet ﷺ: "For whomever I am his Mawla then 'Ali is his Mawla." (Using translation from Tirmidhī 3713)   

أَنَّ النَّبِيَّ ﷺ قَالَ يَوْمَ غَدِيرِ خُمٍّ «مَنْ كُنْتُ مَوْلَاهُ فَعَلِيٌّ مَوْلَاهُ»