whereupon He causes hypocrisy to take root in their hearts, [therein to remain] until the Day on which they shall meet Him" - because they have failed to fulfil the vow which they had made unto God, and because they were wont to lie.

So He hath put as a consequence hypocrisy into their hearts, (to last) till the Day, whereon they shall meet Him: because they broke their covenant with God, and because they lied (again and again).

So He hath made the consequence (to be) hypocrisy in their hearts until the day when they shall meet Him, because they broke their word to Allah that they promised Him, and because they lied.

So He requited them with hypocrisy in their hearts till the day when they meet Him, because they broke their promise with Allah and because they lied.

So He penalized them with hypocrisy in their hearts until the Day they will meet Him - because they failed Allah in what they promised Him and because they [habitually] used to lie.