Surah Taha 20:90

وَلَقَدْ قَالَ لَهُمْ هَـٰرُونُ مِن قَبْلُ يَـٰقَوْمِ إِنَّمَا فُتِنتُم بِهِۦ ۖ وَإِنَّ رَبَّكُمُ ٱلرَّحْمَـٰنُ فَٱتَّبِعُونِى وَأَطِيعُوٓا۟ أَمْرِى

And Aaron had already told them before [the return of Moses], "O my people, you are only being tested by it, and indeed, your Lord is the Most Merciful, so follow me and obey my order."

Translation: Saheeh International

Tafsir

And Aaron had certainly said to them beforehand that is before the return of Moses ‘O my people you are only being tested thereby! But truly your Lord is the Compassionate One so follow me in worship of Him and obey my command’ therein.

Excerpt from Tafsir al-Jalalayn, commentary on 20:90, via Quran.com. The reader has the full commentary and 9 more tafsirs.