The Om Purnamadah Purnamidam mantra is a famous Vedic mantra from the Upanishads.

Here are some of the potential benefits associated with reciting this mantra:

1. Realization of unity: The mantra is believed to help the practitioner realize the fundamental unity of all things in the universe.
   
   
2. Cultivation of inner peace: Reciting the mantra is believed to cultivate a sense of inner peace and tranquillity, helping individuals to cope with stress and anxiety.
   
   
3. Overcoming negativity: The mantra is believed to help individuals overcome negative tendencies and behaviors, and promote a sense of positivity and well-being.
   
   
4. Spiritual growth: The mantra is believed to enhance spiritual growth and understanding, helping individuals to connect with their higher self and the divine.
   
   
5. Release of limitations: The mantra is believed to help individuals release self-limiting beliefs and patterns, and open up to new possibilities in life.
   
   
6. Increased self-awareness: The mantra is believed to help individuals become more self-aware, and cultivate a deeper understanding of their true nature.
   
   

Overall, the Om Purnamadah Purnamidam mantra is considered a powerful tool for personal and spiritual growth, and is believed to bring numerous benefits to those who recite it with sincerity and devotion.

Om! That is infinite (Man), and this (universe) is infinite.
The infinite proceeds from the infinite.
(Then) taking the infinitude of the infinite (universe),
It remains as the infinite (Brahman) alone.
Om! Peace! Peace! Peace!!

ॐ पूर्णमदः पूर्णमिदम् पूर्णात् पूर्णमुदच्यते |
पूर्णस्य पूर्णमादाय पूर्णमेवावशिष्यते ||
ॐ शान्तिः शान्तिः शान्तिः || 

oṃ pūrṇam adaḥ pūrṇam idam pūrṇāt pūrṇam udacyate
pūrṇasya pūrṇam ādāya pūrṇam evāvaśiṣyate
oṃ śāntiḥ śāntiḥ śāntiḥ

The Shanti Mantras or "Peace Mantras" are prayers for Peace (Shanti) found in Upanishads. Generally, they are recited at the beginning and end of religious rituals and discourses.

Shanti Mantras are invoked at the beginning of some topics of Upanishads. They are supposed to calm the mind of the reciter and the environment around him/her. Reciting them is also believed to be removing any obstacles to the task being started.