Overall meaning : When the hypocrites—secret unbelievers who make an outward profession of faith—come to you, Muhammad, they lie to you, saying, ‘We bear witness that you are indeed the Messenger of Allah.’ Allah knows that you are truly His Messenger and He bears witness that the hypocrites are truly liars.
They have taken their false oaths as a shield to be spared death because of their unbelief, and thus they turn others away from the way of Allah. Evil indeed is what they do. That is because they first believed and then renounced their faith; therefore, a seal has been set on their hearts, thus becoming devoid of understanding and right guidance.