“Badi Sādhu Vandana” generally refers to the longer form of Sādhu-vandanā (reverential salutation to monks and nuns) recited during the Avashyaks/Pratikraman in many Shwetambar traditions. Its purpose is:

• to bow with humility to all sadhus–sadhvijis,
• to praise their guṇas (restraint, vigilance, aparigraha),
• and to seek kṣamā (forgiveness) while nurturing maitri and vinay.

Tradition notes

• Shwetambar: Both Laghu (short) and Badi (long) Sādhu Vandana are used; the Badi version is an expanded praise and kṣamā-yāchanā during Vandana in Pratikraman.
• Digambar: Sādhu vandanā is present but verses and order differ; emphasis remains identical—vinay towards munis/āryikās and reflection on their mūlguṇas.

Spiritual essence

• Cultivates vinay (humility) and samyama by prostrating before living ideals of dharma.
• Reduces kashāyas through kṣamā-yāchanā and strengthens aspiration to live like a sadhu.

Related reading from JainKnowledge:

• On Vandana and Pratikraman overview
• “Bhagavānhaṁ ādi vandanā” (a core Vandana sutra) with meaning

If you want, I can share the full original text of the Badi Sādhu Vandana with a simple, line-by-line arth according to your tradition (Shwetambar or Digambar).