UPDATE 2: Here are a few key translations from the audio via AFP:
Our letter is to the Jewish attackers that the killing of our brothers will not stop us from the continuation of jihād.
You won’t have any security calm and our rockets will continue, God willing, if you won’t leave the land of Palestine and you will know that your citizens … are not safe from our members.
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UPDATE: As I surmised below, this was Jamā’at Anṣār al-Sunnah’s first message in Hebrew.
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NOTE: Jamā’at Anṣār al-Sunnah is a global jihadist group based in the Gaza Strip that sympathizes with the al-Qā’idah worldview. Interestingly, this message is in Hebrew. In the forum post as well as the promotion logo below they have it in Arabic and translated into Hebrew, too. Has anyone else seen Jamā’at Anṣār al-Sunnah or any other Palestinian global jihadist group do this before?
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Audio from Jamā’at Anṣār al-Sunnah: “Message to the Enemy”