What is the Resurrection of the Dead ? In Judaism, we believe that in the times of Moshiach (Messiah), the righteous dead ( the unrighteous will not be resurrected ) will be resurrected, and provided an opportunity to live in this ideal world that their acts helped to create.

With this in mind, our Holy Torah relates the necessity to keep the body intact, implying that cremation is problematic. Why? The human body was initially formed from elements of the earth, and so too, when there is a resurrection of dead, as indicated by our holy torah, the resuscitation will also take place from the ground.

In order to facilitate this process on behalf of a loved one, it is imperative that their body is fully intact, and in stellar condition. As such, cremation or any other activity (e.g., autopsies) that would compromise the body, is prohibited (Bi'ur Halachah 311:1 DH v'Chol, Pischei Teshuvah 363:5, Igros Moshe YD 4:56), as it would surely interfere with the resurrection process.

Ones coffin type is also critically important. Only wooden coffins are used, and with no metal (including nails). Why? Because metal coffins or metal materials separate the body from the earth, and hinder it (the body) from eventually melding into the ground, interfering with the resurrection process.