And they were persisting on serious sins.
"The most serious sin" is not utilizing Adhikr, the Great Bounty, as well as the Balance and Trust to keep the universe in its equilibrium, and not giving It to other people of the Messenger’s community for utilization. That is why the hypocrites and their followers became the fuel of Hellfire as explained in verse 2: 39 and 5: 86. The Lord of the universe has taught through His Messenger that the worst among mankind are the Fajir, who are reading the Arabic Qur’an, but are not trying to understand Adhikr, which is made easy to understand by the heart, and thus are darted away from Islam as an arrow is darted away from the bow. Since the hypocrites have been killed by Allah, as explained in verses 63: 4 and 80: 17, they are not mentioned as the worst among mankind. See explanation 8: 22; 66: 6-7; and 98: 6.