Purnamadah Purnamidam

The peace invocation of the Isha Upanishad of the Shukla Yajurveda (it is also placed at the start of the Brihadaranyaka). It says that that (the unseen whole) is full, this (the world) is full, the full comes out of the full, and when the full is taken from the full, the full remains. It is recited at the start of study, rituals and meditation.

Wording checked against: Sanskrit Wikisource: ईशोपनिषत् (invocation and closing repetition) https://sa.wikisource.org/wiki/ईशोपनिषत्; Wikipedia: Shanti Mantras (Purnamadah, with Dayananda Saraswati commentary link) https://en.wikipedia.org/wiki/Shanti_Mantras. Editions differ slightly; follow your family's or guru's version if it differs.