Psalms 106:16

They envied Moses also in the camp, and Aaron the saint of the LORD.

The record to which this verse belongs is that of Israel's wilderness experience, which provides warning lessons and instruction for God's people in the last days and should be studied regularly.
Together with Psalms 105 and 107, it teaches the necessity of appreciating the goodness, mercy, and love of God.
Israel's forgetfulness of God's works led them to envy Moses and Aaron.
That envy was part of a wider rebellion against God's appointed leaders.
The envy was followed by judgment on Dathan's company and the wicked gathered with them.

The verse calls Aaron the saint of the Lord and holy to the Lord, even though he made the idol and announced the feast at Sinai.
His honored position and closeness to God made his participation in Israel's rebellion especially heinous.

While Moses was away, Aaron sanctioned Israel's rebellion by making an idol and announcing a feast.
As God's spokesman who had witnessed God's power and glory, he knew that no image could represent that glory.
God was angry enough to threaten Aaron's life, but Moses' earnest intercession spared him, and through penitence and humility Aaron was restored to God's favor.