Excerpt from ‘Essential Explanation Of The Amita(bha) Sutra As Spoken By The Buddha’ by the Pure Land Tradition’s 9th Patriarch Great Master Ouyi:
Sutra: ‘Sariputra, what do you think? For what reason is that Buddha named “Amita”?’
Explanation: ‘This sutra reveals the wonderful practice of upholding the name [of “Amituofo” (Amitabha or Amitayus Buddha) with profound (i.e. deep) Faith and sincere Aspiration], thus explaining the special characteristics of his name, desiring people to have profound Faith in the inconceivability of the great name of ten thousand virtues, [so as to] wholeheartedly and firmly uphold it, without again having doubts or diversions.
Amita [or “Amituo”], is correctly translated as “Immeasurable”, [which is what] originally cannot be spoken of. Our fundamental teacher [Sakyamuni Buddha], with “light” and “life” as two of its meanings, exhaustibly gathered [and summarised] all [that is spiritually] “Immeasurable.”
The “light” [of Amituofo] thus horizontally pervades the ten directions [i.e. everywhere], and the “life” [of Amituofo] thus vertically exhausts the three times [i.e. past, present and future]. Horizontally and vertically interpenetrating [all space and time], this is the Dharma realm’s [essential] body.
The whole of this [Dharma realm’s] body is Amituofo’s body and [his Pure] Land, likewise is the whole of this [Dharma realm’s] body Amituofo’s name.
Thus, Amituo[fo]’s name, is sentient beings’ true nature of original [i.e. fundamental; intrinsic; inherent potential for complete] enlightenment.
Upholding his name, is [when] initial enlightenment [which begins actualisation of the potential for enlightenment] joins original [enlightenment, which is the potential for enlightenment]. The initial and original are not two, [just as] sentient beings and Buddha[s] are not two [in essence, as both have the same Buddha-nature (i.e. potential to be Buddhas), with the first yet to fully realise it, and the latter having fully realised it].
Thus, [with] one thought corresponding [by sincere mindfulness of Amituofo’s name, is with] one thought [aligned to the] Buddha. [With] thought to thought corresponding, [is with] thought to thought [aligned to the] Buddha.’
Sutra: ‘Sariputra, that Buddha’s bright light is immeasurable, and illuminates the ten directions’ lands without any obstruction. This is why he is named as “Amita[bha: Immeasurable Light]”.’
Explanation: ‘This mind-nature [i.e. Buddha-nature] is still [i.e. at peace], yet always illuminating [with awareness], thus [is it named] as “bright light”. Now having penetrated to realise his mind-nature’s [essential] body’s immeasurability, thus is his bright light immeasurable. [As] all Buddhas have penetrated their mind-nature’s bodies, they all illuminate the ten directions, and can all be named as “Immeasurable Light”. Yet, as within their causal stages, their power of vows are not the same, according to their causes and conditions, they establish different names.
Amituofo as Dharmakara Bhiksu, who gave rose to forty-eight vows, with the vow to have his bright light constantly illuminating the ten directions, now has this fruit accomplished as vowed.
The Dharma Body’s [i.e. all Buddhas’ one collective Dharmakaya] bright light is without division, [distinction or limitation. As] their Reward Bodies’ [i.e. Sambhogakaya(s)] bright lights accord with their true nature [i.e. Buddha-nature], this thus is Buddhas’ paths being the same. [They might have] Manifestation Bodies’ [i.e. Nirmanakayas] bright lights that illuminate one yojana [i.e. about seven miles], ten, a hundred, a thousand yojanas, one world-system, ten, a hundred, or a thousand world-systems.
[As] only Amituo[fo] universally illuminates [everywhere all the time], thus is his other [special] name “Immeasurable Light”. However, the Three Bodies [i.e. Trikaya] are neither one nor different, for enabling sentient beings to attain the four benefits [of the Four Siddhantas (四悉檀), which accord to the listener’s capacity:  worldly method (世间悉檀),  individual method (各各为人悉檀),  curative method (对治悉檀) and  method of the first principle (第一义悉檀)] thus, having these differences.
It should be known that [the Three Bodies are] without obstructions, [only as] restricted by people[‘s conditions], saying [so]. Due to sentient beings and Buddhas having deep conditions [of karmic affinities] thus, where Buddha[s’] light[s] reach[es] in all worlds, there is none who cannot see them completely.
Sutra: ‘Moreover, Sariputra, that Buddha’s lifespan, and that of his people, are of immeasurable and boundless asamkhyeya kalpas. This is why he is named “Amita[yus: Immeasurable Life]”.’
Explanation: ‘[As his] mind-nature illuminates, yet always at peace, thus [is he named] as “Immeasurable Life”. Now having penetrated to realise his mind-nature’s [essential] body’s immeasurability, thus is his lifespan immeasurable.
The Dharma Body’s lifespan is without beginning and without end, [while] Reward Bodies’ lifespans are with beginning and without end. This is likewise Buddhas’ paths being the same, and all [Buddhas] can be named as “Immeasurable Life”. Manifestation Bodies accord with vows and accord with situations, [thus] with extending and hastening not [being] equal.
[As] the King Of Vows Dharmakara [Bodhisattva], has the vow that [himself as a] Buddha and [his] people’s lifespans are all to be immeasurable, now that this fruit has been accomplished as vowed, his other [special] name is “Immeasurable Life”.
“Asamkhyeya”, “boundless”, and “immeasurable” – all these are counting terms, actually having measurable kinds of the immeasurable. However, the Three Bodies are neither one nor different, [as] Manifestation Bodies can also be of the immeasurable kind of immeasurable. “And” (及) means “furthermore”. The people [in Pure Land], refer to [the greatest Bodhisattvas] with Equal Enlightenment [and] returners [i.e. those yet to have any enlightenment]. Speaking of the Buddha’s lifespan, and his people’s lifespans, all are equally immeasurable.
It should be known that the name of [Immeasurable] Light [and Immeasurable] Life, are all originally [upon] sentient beings’ [Buddha-nature] established. With sentient beings and Buddhas [being] equal [in essence, thus is this] able to enable those who uphold the name, [to attain] bright light and [long] lifespan that is the same as the Buddha, without differences.
Once again, due to the meaning of Immeasurable Light, thus are sentient beings born in [the Pure Land Of] Ultimate Bliss already [or promptly] born in the ten directions’ [other Pure Lands too, with] seeing of Amituofo already [or promptly] as seeing all Buddhas of the ten directions, able to deliver themselves, and [to promptly] and universally benefit all [sentient beings].
Due to the meaning of Immeasurable Life, thus are [the Land Of] Ultimate Bliss’ people [those who will attain the Stage Of] One Life To Replacement [of Buddhas], all definitely in this life to accomplish Buddhahood, not reaching [elsewhere to be born as] ordinary beings.
It should be known that apart from this presently manifested one [mindful] thought of Immeasurable Life, [there is no]where [else with] Amituofo’s name. Yet, apart from Amituofo’s name, from where [do we] penetrate and realise this presently manifested one thought of Immeasurable Light and [Immeasurable] Life? May [all] deeply ponder on this, may [all] deeply ponder on this!’
The Sacred Name Of Amituofo 阿弥陀佛之圣号
The Name Of Amituofo Is The Supreme Mantra
Amituofo As One & All Buddhas