Below are quotes from Master Hsuan Hua‘s commentary on The Sutra of the Merit and Virtue of the Past Vows of Medicine Master Vaiḍūrya.

Hsuan Hua, Medicine Master Sutra commentary, p84-85Reciting the Name of Medicine Master Buddha
At the City of Ten Thousand Buddhas, we recite the name of Medicine Master Buddha in the morning and dedicate the merit to the Dharma-protectors of the City, praying that they will be safe from disasters and will enjoy long life. At noon we recite “Namo Fundamental Teacher Śākyamuni Buddha” in order to repay the kindness of Śākyamuni Buddha, who taught the Dharma to us. In the evening we recite the name of Amitabha Buddha, vowing to be born in the Land of Ultimate Bliss, where the three lower paths do not exist. In the Sahā world, we are troubled and afflicted every day, but in the Land of Ultimate Bliss and the Vaiḍūrya Land, there is only happiness.The City of Ten Thousand Buddhas is a new monastery, and we recite the names of three different Buddhas in the morning, at noon, and in the evening. In this respect, we differ from monasteries in China, Hong Kong, Taiwan, Singapore, Vietnam, and other countries where they follow the Chinese Buddhist tradition and recite Amitabha Buddha’s name all the time. When monastics from other places visit the City of Ten Thousand Buddhas, they think that we do everything wrong and do not understand the rules.
We do not claim that what we do at the City of Ten Thousand Buddhas is correct. However, when we rise in the morning, we should emulate the vows of Medicine Master Buddha Who Quells Disasters and Lengthens Life. This will give us the fresh, youthful energy of dawn; an invigorating vitality like that of trees reviving after a drought or a spring bubbling forth from the ground. When we rise at dawn, the fire of our life burns brightly and everything is auspicious. At noon, we should be grateful to Śākyamuni Buddha for all the Dharma and sūtras that he taught us. At night, our thoughts return to the Land of Ultimate Bliss, the final haven where we wish to be reborn.
Hsuan Hua, Medicine Master Sutra commentary, p23-24Two Buddhas, East and West
Śākyamuni buddha came to the Sahā world in order to help living beings resolve the problem of birth and death. He was born into a royal family, but he renounced the wealth of the kingdom and left his home in order to pursue the Truth. After he attained Buddhahood beneath the Bodhi Tree, he contemplated the conditions of living beings in the Sahā world and discovered that we have the deepest affinities with two Buddhas – Medicine Master Vaiḍūrya Light Tathagata in the East and Amitabha Tathāgata in the West. …Although Akṣobhya (Medicine Master) Buddha is in the Vaiḍūrya Land and Amitabha Buddha is in the Land of Ultimate Bliss, both of these Buddhas teach and transform the living beings of the Sahā world. They have deep affinities with each and every one of us. Medicine Master Tathāgata is also known as “Medicine Master Buddha Who Quells Disasters and Lengthens Life;” Amitabha Tathāgata is known as both the “Buddha of Limitless Life” (Amitāyus) and the “Buddha of Limitless Light” (Amitābha).
If you are mindful of Medicine Master Buddha, he will bestow blessings and long life upon you and save you from disasters, illnesses, and offenses. He fulfills the wishes of all living beings. Amitabha Buddha enables beings to be reborn in the Land of Ultimate Bliss. If you wish to be reborn in that land, simply recite Amitabha Buddha’s name. If you wish to be born in the Vaiḍūrya Land, then recite the name of Medicine Master Vaiḍūrya Light Tathagata.
Hsuan Hua, Medicine Master Sutra commentary, p60Magnetic Vows
Every Buddha and Bodhisattva, before achieving Buddhahood, makes infinitely many great vows to benefit and help living beings. When he becomes a Buddha, his vows come true, and, like a magnet, they attract living beings from the ten directions. If his vows are great, then the power of the magnet is great, and no matter how many living beings there are and how heavy their karmic obstacles are, his vows can draw them in. Living beings, despite their ignorance, can sense that he wishes to help them, and so they feel especially close to him. Deep down in their souls they intuitively sense this affinity. In the past, Medicine King Bodhisattva burned his body and gave up his life as an offering to the Buddhas. We, in contrast, can’t even bear to burn a finger, let alone our whole bodies.
Hsuan Hua, Medicine Master Sutra commentary, p62Ordinary Origins of Great Vows
Medicine Master Buddha made this vow in his past lives when he was still cultivating as a bhikṣu; he was no different from you, me, and other living beings then. But because he made great vows, he was able to achieve Buddhahood very quickly. We still haven’t become Buddhas, because we are too selfish, greedy, and quarrelsome, and we don’t want to make great vows.