What is the exact interpretation of Qur'anic verse 3:81 as it seems to suggest that there will be a messenger in every era/age?
Some people are of the view that the covenant was taken by all the prophets including Prophet Muhammad (PBUH) and, therefore, anyone who will prove authenticity of the Book is a messenger. Is that so?
Thank you for your question. This verse speaks of a general principle in terms of a covenant that was taken by all of the prophets to ratify the subsequent prophets. That covenant was also taken from the followers of the prophets, who were to accept the prophets that came after their prophet, and this is what the second part of the verse speaks of.
The context of this verse is within a larger dialog between the Prophet (saw) and the people of the book residing in Medina at the time and he (saw) is the most immediate referent of a subsequent prophet that the followers of previous prophets should accept.
While the general purport of the verse is that all of the prophets took the covenant, no prophet will be sent after the final Prophet, Muhammad (saw) as the Qu'ran itself confirms (see 33:40) and as such him taking the covenant would not be for the purpose of confirming an actual prophet after him.
May you always be successful.