Given the question: Question: "what is considered the ultimate expression of compassion?"  Context: "Traditionally, the first step in most Buddhist schools requires taking refuge in the Three Jewels (Sanskrit: tri-ratna, Pāli: ti-ratana)[web 19] as the foundation of one's religious practice. The practice of taking refuge on behalf of young or even unborn children is mentioned in the Majjhima Nikaya, recognized by most scholars as an early text (cf. Infant baptism). Tibetan Buddhism sometimes adds a fourth refuge, in the lama. In Mahayana, the person who chooses the bodhisattva path makes a vow or pledge, considered the ultimate expression of compassion. In Mahayana, too, the Three Jewels are perceived as possessed of an eternal and unchanging essence and as having an irreversible effect: "The Three Jewels have the quality of excellence. Just as real jewels never change their faculty and goodness, whether praised or reviled, so are the Three Jewels (Refuges), because they have an eternal and immutable essence. These Three Jewels bring a fruition that is changeless, for once one has reached Buddhahood, there is no possibility of falling back to suffering."  Answer:
The answer is:
bodhisattva path