(73) “Those who disbelieve are allies of one another. Unless you do so, there will be turmoil in the land and great corruption.”

Having established the bond of allegiance among the believers, Allah states that, since disbelief unites the disbelievers, they are allies of one another (1). Thus, no one takes them as allies except a disbeliever like themselves.

His words, “Unless you do so,” mean: unless you take the believers as allies and treat the disbelievers as enemies. This would occur if you took them all as allies, treated them all as enemies, or took the disbelievers as allies and treated the believers as enemies.