قَالُوا۟ لَن نَّبْرَحَ عَلَيْهِ عَـٰكِفِينَ حَتَّىٰ يَرْجِعَ إِلَيْنَا مُوسَىٰ Qur’an Ta-Ha (20:91)Q a loo lan nabra h a AAalayhi AA a kifeena h att a yarjiAAa ilayn a moos a
Obviously Aaron's speech in the last verse, and the rebels' defiance in this verse, were spoken before the return of Moses from the Mount.
The rebels had so little faith that they had given Moses up for lost, and never expected to see him again.