يَـٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوا۟ ٱتَّقُوا۟ ٱللَّهَ وَكُونُوا۟ مَعَ ٱلصَّـٰدِقِينَ
“O believers! Be mindful of Allah and be with the truthful.”
Closes the passage on Ka'b, Murara and Hilal's repentance with a command to stand with the truthful.
The closing exhortation of the passage revealed over Ka'b ibn Malik RA's repentance, calling believers to be with the truthful.
This is the specific, extremely well-documented asbab al-nuzul: Ka'b ibn Malik's own account (quoted in the post) of Allah's mercy after 50 days of being shunned -- the direct occasion for this ayah's revelation.