From the Question & Answer of the Ameer of Hizb ut Tahrir, Ata Bin Khalil Abu al-Rashtah - Part 10 Excerpts

Question: In the book At-Tafkeer Al-Islami, which is one of the adopted books, it mentions that supplication (du’aa) does not turn back the Divine Destiny (qadar) and does not change the Divine fate (qadaa’) or the knowledge of Allah (swt)). However there are texts from the Qur’an and the Sunnah that seem to me to contradict this understanding; it has been narrated that the Prophet (saw) said:

In our books we find the narration of Saad bin Moaz’s verdict on the Jews of Bani Qurayza; to kill their men and confiscate their money and take their women as captives, although the decisive rule on the prisoners of war in the Qur’an is either Mann (kindness) or Fida (ransom): Is this ruling by Saad in contradiction with the rule of the Qur’an and thus we must drop this…

In the book of the “Islamic Personality” Volume III (The Origins of Jurisprudence), under the section "There is no ruling before the statement of the Shar’’" on page 28 (Arabic), I quote the text: “There is no action from man, or anything related with man’s action, except that it has a ruling in Shariah, and there is no ruling except by the presence of an evidence related to it specifically…