Ali 'Imran 3:72

Some from among the people of the Book chose a strategy of deception in order to mislead Muslims. According to their agreed plan, they would declare their belief in the Qur'an in the morning and then reject it in the evening. They thought that this quick about-turn would create doubts in the minds of Muslims about Qur'an and Islam and they might turn away from their faith thinking that there must be something wrong with Islam visible to such learned people who were open-minded enough to accept it first. They also made it a point to re-serve their feinted declaration of belief in Islam to hoodwink Muslims only! Their true belief, they planned, would be affirmed before none but only those who follow their own creed. The rule was: Sincerity with the later, expediency with the former!

That these tricks are low is proved later in Verse 73 when the Holy Prophet ﷺ has been asked to declare that their clever moves are not going to work for them since Guidance given to servants of Allah is certainly from Allah. So, it is He who, with Guidance in His control, can make whoever He will steadfast on that Guidance. No one can succeed in weaning such a person away from it with any trick, plan or enticement whatsoever.

The reason why they act in the way they do is envy, that is, they envy Muslims as to why they were given the Scripture, or they envy their supremacy in religious argument. It is because of this envy that they keep working to bring about the downfall of Islam and of the community that adheres to it.

That this envy is based on not knowing the nature, timing and wisdom of Allah's grace and mercy is explained in the later part of verse 73 and in verse 74.