Often, people interested in astrology are interested in spirituality in general as well. Therefore astrologers often receive questions on this subject.
The fire triangle (houses 1, 5, and 9) represent different facets of religion and morality. The water triangle (houses 4, 8, and 12) represent different facets of the personal spiritual quest.
In the fire triangle, the first house pertains to personal character and individual morality. The fifth house pertains to the ability to practice, understand and learn moral and religious disciplines. The ninth house represents ones relationship to gurus, guides, etc. as well as to religion and religious institutions as well as the entire attitude towards philosophical subjects in total.
In the water triangle the eighth house represents mystical powers and ability to see the unseen or “occult” reality in the world (“siddhi”). The twelfth house pertains to ones humility and detachment from physical and worldly affairs, as well as the logic and knowledge which supports such attitudes (“jnana”). The fourth house – domain of the innermost self – pertains the the ultimate goal, self-realization and to the sublime understanding of the role of emotions in a spiritual setting (“bhakti”).
The sixth has been ascribed to “yoga” but this is mainly in the health-supporting sense of that word.
Among planets, look particularly at Ketu.