2/43 — Three commands
The first two commands are familiar; the third is striking. It does not say "bow" — it says "bow with those who bow".
What is asked, that is, is not only that the act of worship be performed but that it be performed together. At the beginning of the sūra the prayer was to be "kept up" (held standing); here a communal dimension is added to that. The measure we saw in the plural of al-Fātiḥa's "You alone do we serve" turns here into a command.
The meaning of this command within its context also matters: the ones addressed are a community that has received a book but is divided. That the command given to a divided community should be "bow together" is no coincidence.