Riyad Us-Saliheen (Gardens of the Righteous)

Chapter 283
Prohibition of Chastisement with Fire

1609. Abu Hurairah (May Allah be pleased with him) said: The Messenger of Allah (PBUH) sent us on an expedition and said to us, "If you find so-and-so (he named two persons belonging to the Quraish) commit them to the fire.'' When we were on the verge of departure, he said to us, "I ordered you to burn so-and-so, but it is Allah Alone Who punishes with the fire. So if you find them put them to death.''
[Al-Bukhari].

Commentary:  The Prophet (PBUH) has clearly stated that no one is to be burnt in any case, not even an enemy.

1610. Ibn Mas`ud (May Allah be pleased with him) reported: We were with the Messenger of Allah (PBUH) in a journey when he drew apart (to relieve nature). In his absence, we saw a red bird which had two young ones with it. We caught them and the red mother bird came, beating the earth with its wings. In the meantime the Prophet (PBUH) returned and said, "Who has put this bird to distress on account of its young? Return them to her.'' He (PBUH) also noticed a mound of ants which we had burnt up. He asked, "Who has set fire to this?'' We replied: "We have done so.'' He (PBUH) said, "None can chastise with fire except the Rubb of the fire.''
[Abu Dawud].

Commentary:
1. To catch nestlings of a bird and torment them or to burn the holes of insects along with their inmates is forbidden. One can, however, burn their vacant holes.

2. If somebody has burnt a person to death, it is not permissible to kill him in return by burning. If the heirs of the victim want to kill him in the same way under Al-Qisas (the law of equality in punishment) they can do so; otherwise he can be put to the sword.