Not Enunciating Hashem's Name as It Is Written

From Halachipedia

Saying Hashem's Name as It Is Written

  1. It is forbidden to recite Hashem's name as it is written. In fact, Chazal state that it is such a grave sin it is punished with the loss of one's share in the World to Come.[1]

Abaye Hava Mesader

  1. When recite Abaye Hava Omer, some say that a person should be careful to pause between the words Abaye and Hava since saying them quickly together sounds like the enunciation of Hashem's name as it is written. Others say that it is permissible since one doesn't intend to enunciate Hashem's name. It is preferable to pause[2] or skip the word Hava altogether.

Saying the Letters

  1. Just as it is forbidden to recite Hashem's name as it is written, it is similarly forbidden to enunciate the letters of Hashem's name, Yud Hey Vav Hey.[3]

Regarding the Shem Yichud see Leshem_Yichud#Reciting_Hashem.27s_Name

Sources

  1. Sanhedrin 90a
  2. halachayomit.co.il
  3. Yabia Omer OC 9:12