وَيُفْتَحُ بِإِلْحَاقِ أَلِفِهَا، نَحْوَ: «يَا زَيْدَا!».
Translation: The text also records a form of appeal with an added alif, e.g. “Yā Zaydā!”.
This is a special form of appeal. Do not treat the final alif as equivalent to the spelling of an ordinary accusative indefinite with tanwīn.