Narrated Sad:
Allah’s Apostle set out for Tabuk. appointing ‘Ali as his deputy (in Medina). ‘Ali said, “Do you want to leave me with the children and women?” The Prophet said, “Will you not be pleased that you will be to me like Aaron (Harun) to Moses (Musa)? But there will be no prophet after me.”
Translated by some like this: (‘Your relation to me shall be like the relation of Harun to Musa…) & (You hold in relation to me the same position as Harun held in relation to Musa)
Hadith in Arabic:

عَنْ مُصْعَبِ بْنِ سَعْدٍ عَنْ أَبِيهِ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ خَرَجَ إِلَى تَبُوكَ وَاسْتَخْلَفَ عَلِيًّا فَقَالَ أَتُخَلِّفُنِي فِي الصِّبْيَانِ وَالنِّسَاءِ قَالَ أَلَا تَرْضَى أَنْ تَكُونَ مِنِّي بِمَنْزِلَةِ هَارُونَ مِنْ مُوسَى إِلَّا أَنَّهُ لَيْسَ نَبِيٌّ بَعْدِي

Sahih al Bukhari
Volume 5, Book 59, Number 700: