From https://dafyomireview.com/hidden_tzadikim.php?d=9: Chilazon Rabeinu once said regarding the Chilazon by the Machon Mikdash. He said that he checked this with spiritual vision and physical vision and it is indeed the Chilazon used to make the techelet (blue dye). He bought from them Chilazons and asked his students to dye for him strings of techelet. One…
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