Ibnul-Qayyim Al-Jawziyyah (rahimahullaah) said:
And mankind, with regard to their performance of prayer are in five levels:
The First: The level of the one who is negligent and wrongs his soul: He is the one who falls short in performing wudu (ablution) properly, performing the prayer upon its time and within its specified limits, and in fulfilling its essential pillars.
The Second: The one who guards his prayers upon their proper times and within their specified limits, fulfils their essential pillars and performs his wudu with care. However, his striving (in achieving the above) is wasted due whisperings in his prayer so he is taken away by thoughts and ideas.
