They swear by Allah that they did not speak , and certainly they did speak , the word of unbelief , and disbelieved after their Islam , and they had determined upon what they have not been able to effect , and they did not find fault except because Allah and His Apostle enriched them out of His grace ; therefore if they repent , it will be good for them ; and if they turn back , Allah will chastise them with a painful chastisement in this world and the hereafter , and they shall not have in the land any guardian or a helper .