Had it not been for a decree from God that had already gone forth, there would indeed have befallen you a tremendous chastisement on account of all [the captives] that you took.

Had it not been for a previous ordainment from God, a severe penalty would have reached you for the (ransom) that ye took.

Had it not been for an ordinance of Allah which had gone before, an awful doom had come upon you on account of what ye took.

Were it not for an ordinance from Allah that had gone before, surely there would have befallen you a great chastisement for what you were going to do.

If not for a decree from Allah that preceded, you would have been touched for what you took by a great punishment.