Swami Dayanand ji has mentioned four properties of the Yagya material in the Yajurveda commentary and other self-written texts:
अग्निहोत्रमारभ्याश्वमेधपर्यन्तेषु यज्ञेषु सुगन्धिमिष्टपुष्टरोगनाशकगुणैर्युक्तस्य सम्यक् संस्कारेण शोधितस्य द्रव्यस्य वायुवृष्टिजलशु(िकरणार्थमग्नौ होमो क्रियते, स तद्वारा सर्वजगत् सुखकार्येव भवति।
In the rituals from Agnihotra to Ashwamedha, Yagya must be performed in four types of substances having properties as mentioned below-
Aromatic properties- Kasturi, Saffron, Agar, Tagar, White sandalwood, Cardamom, Nutmeg, Mace etc. (Nagarmotha, Balchhad, Khus, Clove, Tumul, Tejpat, Talispatra, Guggul, Sugandhabala, Sugandhakokila, Kulanjan, Mulethi, Hauber etc. are also aromatic substances).
Sweet properties-Sugar, Honey, Dates, Dry grapes, Raisins and Mohanbhog, Sweet rice, Laddus, etc.
Nourishing properties-Ghrita, Milk, Fruits, Tubers, Grains, Almonds, Cashew nut, Pistachios etc.
Theraupeutic properties-Somlata (Giloyd), Brahmi, Absinthe, Harad, Camphor powder, Shatavar, Adusa, Root of Indrayana, Deodaru, Punarnava, Kshirkakoli, Shalparni, Makoy, Amla, Khubkala, Gokhru, Rasna, Rose flower, Jeevanti, Pandari, Vaivadang etc.
The Yagya, which is performed in the fire, by combining the substances having these four properties with inter-purification, arrangement and appropriate blending, helps in purifying the air and rain water. This brings happiness to the whole world.