Sefer Yetzirah 2:3
ספר יצירה נוסח הגר"א ב׳:ג׳
Sefer Yetzirah Gra Version 2:3
The passage presents a classification of the twenty-two Hebrew letters into five articulatory groups according to where they are produced in the mouth: gutturals (throat), palatals (palate), linguals (tongue), dentals (teeth), and labials (lips), with Samekh and Shin both grouped among the dental letters.
עשרים ושתים אותיות יסוד חקקן בקול חצבן ברוח קבען בפה בחמשה מקומות אחה"ע בגרון גיכ"ק בחיך דטלנ"ת בלשון זסשר"ץ בשינים בומ"ף בשפתים:
Twenty-two Foundation Letters/ He engraved them with voice/ He carved them with breath/ He set them in the mouth/ In five places/ Alef Chet Heh Eyin (אחהע) in the throat (Gutturals)/ Gimel Yud Kaf Kuf (גיכק) in the palate (Palatals)/ Dalet Tet Lamed Nun Tav (דטלנת)/ in the tongue (Linguals)/ Zayin Samekh Shin Resh Tzadi (זסשרצ)/ in the teeth (Dentals)/ Bet Vav Mem Peh (בומפ) in the lips. (Labials)