Sūtra on Upāsaka Precepts, Chapter 20
The Three Pure Refuges
“Good sons, just as the Buddha, pratyekabuddhas, and śrāvakas are different, the Three Jewels cannot be alike. What are the differences? They are in the initial resolve, adornment, attainment of the path, and nature."
Excerpts from A Discourse on the Sūtra on Upāsaka Precepts
Venerable Xiao Pingshi
There are major differences between the Buddha, pratyekabuddhas, and śrāvakas.
The initial resolve at the causal ground of the Three-Vehicle saints is already different. For sound-hearer (śrāvaka) saints, their initial resolve to invoke the bodhicitta mind, from the first to the fourth fruition, is to transcend the cycle of birth and death in the three realms and never return to these realms. What they initially learned from the Buddha was the cultivation of the Four Noble Truths and Eightfold Paths and observing the Four Foundations of Mindfulness. While the initial resolve of solitary-realizers (pratyekabuddhas) at the casual ground is also to transcend the cycle of birth and death, they practice the Twelve Links of Dependent Arising on their own rather than from all Buddhas. Notably, the initial resolve of buddhas is entirely different from that of the śrāvakas and pratyekabuddhas. Although the initial resolve of all buddhas is to transcend transmigration, all buddhas resolve to benefit from it and to help all sentient beings attain transcendence, thereby enabling them to perfect the ultimate Path of Buddhahood.
The second difference is in the adornments. The only adornment attained by cultivating the teachings of śrāvakas and pratyekabuddhas is liberation from the cycle of birth and death. The dharma adornment of the Two Vehicles is entirely different as they are not as grand, profound, expansive, and wondrous as the teachings of bodhisattvas. As such, arhats and pratyekabuddhas would not have similar adornments as bodhisattvas, including being dressed similarly to bodhisattvas and having adherents, families, and treasures, like bodhisattvas.
The third difference is in the attainment. Bodhisattvas cultivating the Path toward Buddha Bodhi will become buddhas in the future, whereby they fully possess adornment of both transmundane and mundane dharmas. Buddhas and One-Vehicle disciples will propagate solely the Mahayana Dharmas. For the Two-Vehicle disciples, the Sound-Hearer and Solitary-Realizer Vehicle dharmas are sometimes combined into one dharma, and the Mahayana dharmas are also spoken. The Three-Vehicle disciples might talk about the different dharmas of the Three-Vehicle Bodhi, but sound-hearer saints have only sound-hearer disciples, not solitary-realizer or bodhisattva disciples (due to their different attainment levels, they cannot teach higher-level dharmas). Solitary-realizer saints (due to their mindsets of being solitary) do not have any solitary-realizer, sound-hearer, or bodhisattva disciples.
The fourth difference is in the mindsets. The Two-Vehicle adept (aśaikṣa) saints will definitely never return to the three realms. Once liberated, they will never gain rebirth in the three realms after passing away. Their mind-nature would have been thus determined. Pratyekabuddhas will never preach any dharmas; arhats will preach dharmas to sentient beings to some extent as their mind-nature wishes to dwell only in a state of loneliness. However, bodhisattvas are entirely different. If we ask dharmas from bodhisattvas, they will answer with abundance, even forcefully at times, regardless of and at all costs. Their mindsets are altogether different from those of the Two-Vehicle saints.
Therefore, based on these main differences, the Buddha Bodhi is naturally divided into drastic distinctions of the Three Vehicles.
A Discourse on the Sūtra on Upāsaka Precepts, Vol. 6, pp. 220-225