Bragging over one's accomplishments or taking credit for what he has not done is common behavior for many members of society. Yet, the fact remains that it is blameworthy in the Sight of Allah:
Those who exult in what they have done and love to be praised for what they have not done should not suppose that they have escaped the punishment. They will have a painful punishment. (Surah Al ‘Imran; 188)
Perverted attitudes such as pride in an accomplishment that was actually achieved by Allah's will underlie such behavior, in spite of the fact that whenever a deed is done, it is Allah, the All-Mighty, Who has willed it and carried it out. No individual has any independent power of his own. Everything happens by Allah’s permission and will. Consequently, this kind of conceit reveals a person’s incapability to appreciate Allah with properly, and further, it means considering oneself an equal to Allah (Allah is surely beyond that). The Qur’an states that ascribing partners to Allah is the greatest sin and, unless one repents of it, he will not be forgiven.