﴿فَاسْتَقِيمَا وَلَا تَتَّبِعَانِّ﴾
So remain steadfast, both of you, and do not follow. (Yūnus 10:89, in the well-known recitation)
The expression wa-lā tattabiʿānni functions as a prohibition. Its wāw should not automatically be treated as the circumstantial wāw of an ordinary negative declarative clause. One issue is when a negative imperfect reporting a state permits wāw; another issue is the coordination of two distinct instructional acts. The syntactic and pragmatic functions must be kept apart.