Assalaamu alaykum. I want to know the authenticity of this hadithabout killing the frogs?
It was also reported from Anas, may Allaah be pleased with him, that the frog took water in its mouth to put out the fire that was prepared to burn the Prophet Ibrahim (Abraham), may Allaah exalt his mention.
Wassalaam

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, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

The relevant report that we found was cited by As-San‘aani in his book Subul As-Salaam. He said that Anas narrated, "Do not kill frogs; they passed by the fire that was prepared to burn Ibraaheem (Abraham) and took water in their mouths to spray it over the fire."

After careful research, we could not find a hadeeth with this very wording. Even the commentators who revised As-San‘aani's book, i.e. Taariq ‘Awadhallah and Muhammad Hallaaq, refrained from classifying this report as authentic or inauthentic contrary to their methodology throughout the book. Perhaps this is because they could not find the opinion of Hadeeth scholars regarding it. The closest report is the one cited by ‘Abd Ar-Razzaaq in his book Al-Musannaf. It reads: "Abu Sa‘eed Ash-Shaami narrated on the authority of Abaan from Anas ibn Maalik that he said, "The Prophet, sallallaahu ‘alayhi wa sallam, said, 'Give safety to the frog, for its croaking that you hear is Tasbeeh, Taqdees, and Takbeer. The animals sought the permission of Allah to extinguish the fire into which Ibraaheem was thrown, and He gave permission to the frogs; they filled their mouths with water and tried to put the fire out. As a reward, Allah substituted the heat of the fire with water for them.'"

However, we could not find any scholar of Hadeeth classifying this report as authentic or inauthentic. This hadeeth's chain of narration is very weak, and therefore some contemporary scholars classified it as very weak. ‘Abdullah Al-‘Utaybi wrote, "Its chain of narration is very weak." [Al-Lubaab Sharh Fusool Al-Aadaab]

A similar report was cited in Tareekh Dimashq by Ibn ‘Asaakir on the authority of  Ibraaheem ibn Abi Yahya Al-Madeeni, from a man from Al-Asbagh ibn Nubaatah, from ‘Ali ibn Abi Taalib, that he said:

"The mules reproduced faster, and they were among the animals that hastened to carry the firewood to burn Ibraaheem, so he supplicated against them and Allah stopped them from producing offspring. The frogs lived in tunnels; they filled their mouths with water and tried to put the fire out, so Ibraaheem supplicated Allah for them, and they were made to live in the water. The gecko, on the other hand, blew at the fire (to keep it burning). Geckos used to be the best among animals, so he cursed them and they became cursed, and whoever kills any of them is rewarded."

Al-Maqreezi mentioned this report in Al-Muqaffi Al-Kabeer (1/25) and said, "This chain of narration is unacceptable; Al-Asbagh ibn Nubaatah and Ibraaheem ibn Yahya were both classified as Matrook narrators (one whose narrations are rejected because he is suspected of falsehood or is openly wicked in speech and action or is guilty of carelessness or frequent wrong notions)."

In brief, the report in reference is inauthentic and cannot be attributed to the Prophet, sallallaahu ‘alayhi wa sallam. However, killing the frog was forbidden in other ahaadeeth without the reason mentioned in this report.

Allah knows best.