It is common to understand that the only way we can know ourselves is through looking inside or within, which is very hard and I have not found anyone give a guaranteed proof that they have been able to do it, but the typical method is meditation so below is how major religions do it.
1. Hinduism: Dhyana & Yoga MeditationPractices: Dhyana (deep contemplation), mantra chanting (e.g., "Om"), Kundalini yoga, Bhakti (devotional meditation).
Purpose: Union with the divine (Brahman), liberation (moksha), self-realization (atman).
Key Texts: Bhagavad Gita, Upanishads, Patanjali's Yoga Sutras.
Buddhism: Mindfulness & Insight (Vipassana)Practices: Mindfulness (Satipatthana), Vipassana (insight meditation), Metta (loving-kindness), Zen (Zazen).
Purpose: Awakening (nirvana), ending suffering, understanding impermanence.
Key Texts: Dhammapada, Pali Canon, Mahayana Sutras.
2. Jainism: Samayika & Preksha DhyanaPractices: Focus on nonviolence, breathing, and inner awareness.
Purpose: Liberation of the soul (moksha) from karmic bondage.
Special Feature: Strict mental discipline and detachment.
Christianity: Contemplative Prayer & CenteringPractices: Lectio Divina (sacred reading), silent prayer, Centering Prayer, Rosary.
Purpose: Communion with God, inner stillness, divine love.
Mystics: Teresa of Avila, St. John of the Cross, Thomas Merton.
3. Islam: Dhikr & Sufi MeditationPractices: Dhikr (remembrance of God through repetition), Muraqabah (watchfulness), Sufi whirling.
Purpose: Union with the divine, purification of the heart (Tazkiyah).
Sufi Influences: Rumi, Al-Ghazali, Ibn Arabi.
4. Judaism: Hitbodedut & Kabbalistic MeditationPractices: Hitbodedut (personal prayer and solitude), meditating on Hebrew letters and divine names.
Purpose: Closeness to God (Devekut), self-reflection, spiritual insight.
Mystical Path: Kabbalah, Hasidic traditions.
5. Sikhism: Naam Simran & Shabad KirtanPractices: Repetition of God's Name (Naam Japna), devotional singing (Kirtan), silent reflection.
Purpose: Merge with Waheguru (God), ego transcendence.
Scriptures: Guru Granth Sahib.
6. Taoism: Zuòwàng & QigongPractices: Sitting and forgetting (Zuòwàng), energy flow meditation, breathing techniques.
Purpose: Harmony with the Tao (the Way), inner balance, natural flow.
Texts: Tao Te Ching, Zhuangzi.
6. Indigenous & Shamanic TraditionsPractices: Trance, drumming, vision quests, nature meditation, ancestral connection.
Purpose: Connection with spirits, nature, ancestors, and healing.
So we can classify that the Unified Themes across Religions are:
Breathe Awareness: Common in Buddhism, Hinduism, Taoism, and more.
Repetition of Words/Sounds (Mantra/Dhikr): Seen in Hinduism, Sikhism, Islam, and Christianity.Silence & Stillness: Valued in Christian mysticism, Sufism, Zen.
Love & Compassion: Central in Metta, Christian agape, Sufi love.
Union with the Divine: Core goal in nearly all traditions.