Whether offender is alive when crucified for Hiraabah
3-1-2017 | IslamWeb
Question:
In Islam, sometimes crucificition is part of the disciplinary actions, does the crucifiction come after the killing in order to display what happens to criminals, or are they alive when they are crucified in order to illustrate it in an even stronger way?
Answer:
All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.
Crucifixion was prescribed as a punishment for Hiraabah (banditry or terrorizing people); Allah, The Exalted, says (what means): {Indeed, the penalty for those who wage war against Allah and His Messenger and strive upon earth (to cause) corruption is none but that they be killed or crucified or that their hands and feet be cut off from opposite sides or that they be exiled from the land. That is for them a disgrace in this world; and for them in the Hereafter is a great punishment.} [Quran 5:33]
Scholars held different views regarding the manner of crucifixion in this context. Ash-Shinqeeti 
commented on the verse saying, "Scholars held different views on the crucifixion mentioned in the verse. Some maintained that the offender should be crucified alive and starved to death. Others held that he should be crucified alive and then killed with a spear while crucified. Others maintained that he should be killed first and then crucified..." [Adhwaa' Al-Bayaan]
Ash-Shawkaani wrote, "The apparent indication of the verse is that the offender should be crucified alive and left as such until death because it is one of the options (other than killing) set by Allah for such a crime. Some held that the offender should be killed first and then crucified and that it is impermissible to crucify him before death and thus deny him food, drink, and performing prayers. The answer (to them) is that it is a punishment prescribed by Allah in His Book for people." [Fat-h Al-Qadeer]
It should be noted that the punishment of the Hiraabah is a Hadd (corporal punishment set by the Sharia) and not Ta‘zeer (disciplinary punishment).
Allah knows best.