What does the Bible say about cremation?
As far as the Bible is concerned, there is no text that prohibits cremation. However, we can generally see in the Bible that the preferred way of treating the dead is burial.
Let us consider the following situation:
Jonathan was cremated
1Sa 31:2 And the Philistines followed hard upon Saul and upon his sons; and the Philistines slew Jonathan, and Abinadab, and Malchishua, Saul's sons.
1Sa 31:8 And it came to pass on the morrow, when the Philistines came to strip the slain, that they found Saul and his three sons fallen in mount Gilboa.
1Sa 31:9 And they cut off his head, and stripped off his armour, and sent into the land of the Philistines round about, to publish it in the house of their idols, and among the people.
1Sa 31:10 And they put his armour in the house of Ashtaroth: and they fastened his body to the wall of Bethshan.
1Sa 31:11 And when the inhabitants of Jabeshgilead heard of that which the Philistines had done to Saul;
1Sa 31:12 All the valiant men arose, and went all night, and took the body of Saul and the bodies of his sons from the wall of Bethshan, and came to Jabesh, and burnt them there.
1Sa 31:13 And they took their bones, and buried them under a tree at Jabesh, and fasted seven days.
Albert Barnes commented, "Burning was not the usual mode of sepulture among the Hebrews. But in this case from a pious desire to disguise the mutilation of the headless corpses, and exempt them from any possible future insult, the men of Jabesh burned the bodies, yet so as to preserve the bones."
Christian martyrs were burned
What the living would do to the body of the dead may go against the will of the dead person. Nevertheless, it will be unjust for a righteous person who dies if his or her final destination will be hellfire simply because of being cremated.