Final answer:
The action of placing the forehead onto a piece of hardened clay from Karbala or Najaf during prayer is known as Sajdah. This practice is a significant part of Shia Muslim prayers and is linked to the reverence of these holy cities.
Step-by-step explanation:
The action of placing the forehead onto a piece of hardened clay (turba) from Karbala or Najaf during prayer is called Sajdah. The clay piece serves as a symbol of humility and devotion during prayer for Shia Muslims. It is especially significant because Karbala and Najaf are revered as holy cities in Shia Islam; Najaf is home to the tomb of Imam Ali and Karbala is the site of the martyrdom of Imam Husayn, the grandson of the Prophet Muhammad. The Sajdah is an integral part of the Salat—the worship in the form of prayer—which is one of the Five Pillars of Islam. The other options provided: Tawaf refers to the circumambulation of the Kaaba during the Hajj pilgrimage, Istikhara is a prayer for seeking guidance, and Ziyarat pertains to the visitation of holy sites.