Was not the repentance of Tha'labah ibn Hatib, who withheld zakat, accepted after he returned to the Messenger of Allah, peace and blessings be upon him, to pay it, and likewise the repentance of the hypocrites who lagged behind from the expedition and then wanted to go out on it?

The widely circulated story about Tha'labah ibn Hatib is incorrect, as he participated in Badr, and the sins of the people of Badr were forgiven. As for the hypocrites who refused to participate in the غزوة (military expedition), they did not repent; rather, they disbelieved and died in wickedness. Allah commanded His Prophet, peace and blessings be upon him, not to pray over them or stand by their graves.