Nasai

1204. Commentary: By "command" is meant concession and permission, because both of these are harmful creatures, and a harmful creature should be killed before it causes harm. If one does not kill them, then throughout the prayer one's attention will remain focused on the snake or scorpion, and this will cause disturbance in the prayer. Therefore, there is a concession that snakes and scorpions may be killed. As for the question of whether the prayer of the one praying will be invalidated by this act of killing or not, a group of scholars, in view of the wording of the hadith, have stated that this does not invalidate the prayer. The author of "Subul al-Salam" says: "This hadith is evidence that whatever action is unavoidable for their killing does not invalidate the prayer, whether that action is minor or major." See: [سبل السلام ، باب شروط الصلاة]

921. Commentary:
These are animals that cause harm to humans; therefore, having pity on them is an injustice to humans. Thus, even during prayer (salah), they should be killed. Whether one has to turn away from the direction of the qiblah in order to find a stick or stone, or to chase after the animal, it is permissible. Some scholars say that in this latter case, the prayer becomes invalid and must be repeated. However, some other scholars, by analogy with the prayer of fear (salat al-khawf), consider the prayer to remain valid. «والله اعلم»

Benefits and Issues:
➊ The reason for the command to kill a snake or scorpion during prayer is that these are extremely harmful creatures. If they escape, it is possible that they may not come under control again and may harm someone. Therefore, it is necessary to kill them immediately.

➋ In such situations, if the person praying leaves his place and walks to fetch a stick or something similar to kill the creature, this is a necessity. Therefore, this does not break the prayer. He should resume the prayer from where he left off.

➌ There are also several other actions which are reported from the Noble Prophet (sallallahu alayhi wa sallam) or the noble Companions (radi Allahu anhum ajma'in) as having been done during prayer. Due to these actions as well, the prayer will not become invalid. For example: replying to a greeting with a gesture, carrying a child while praying, stopping someone from passing in front, etc.

Lexical Explanation:
«اَلْحَيَّةَ» means snake.
«اَلْعَقْرَبَ» means scorpion. Both are in the accusative case due to being objects of «أَسْوَدَيْنِ». By «أسودين» is meant both the snake and the scorpion, regardless of their color. It is not necessary that their color must be black.

Benefits and Issues:
➊ This hadith proves that killing a snake or scorpion during prayer does not invalidate the prayer.
➋ It is also understood that killing these two harmful creatures is necessary.
➌ The majority of scholars hold the opinion that killing a snake or scorpion during prayer does not render the prayer invalid.
➍ Imam Tirmidhi rahimahullah has also reported from some people that it is disliked, but in light of the evidences, the decision of the majority is correct. See: [جامع الترمذي، الصلاة، باب ماجاء فى قتل الأسودين فى الصلاة، حديث : 390]