One of the most outstanding characteristics of mindfulness of Buddha (念佛) is that it enables swift birth in Amitā[bha] Buddha’s (Āmítuófó: 阿弥陀佛) Pure Land (净土) within this life (if one with profound faith and sincerely aspiration practises accordingly). Upon reaching the Pure Land, one is able to swiftly progress towards Buddhahood, without backsliding or obstacles in between. It is truly the expressway to Buddhahood.
For ordinary beings (凡夫) to become Buddhas without the Pure Land path, there is need to go through 52 stages of Bodhisattva attainments (菩萨五十二位) – the 10 Faiths (十信), 10 Abodes (十住), 10 Practices (十行), 10 Transferences (十回向), 10 Grounds (十地) and Equal Awakening (等觉; highest Bodhisattvahood), before reaching Supreme Enlightenment (妙觉; Wonderful Awakening; Buddhahood). In terms of time, this requires 3 Great Asaṃkhyeya-Kalpas (三大阿僧祗劫). (1 Asaṃkhyeya-Kalpa is 100, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000 Mahā-Kalpas (or 1048 Mahā-Kalpas), while 1 Mahā-Kalpa (大劫) is 1, 343, 840, 000 years, with 3 Great Asaṃkhyeya-Kalpas thus being 1, 343, 840, 000 x 1048 years.] As this calculation is from the first stage of the 10th Abode (初住) onwards, the time spent for prior unsubstantial or trial-and-error backsliding practice that is difficult to calculate is not added yet! As such, the time needed for such ordinary beings to practise to become a Buddha is much longer than 3 Great Asaṃkhyeya-Kalpas.
However, from the Amitābha Sūtra《阿弥陀经》, we know that Āmítuófó attained Buddhahood (and created his Pure Land) only 10 Mahā-Kalpas (13, 0 43, 840, 000 years) ago. This is tremendously shorter than 3 Great Asaṃkhyeya-Kalpas. Yet, according to the sūtra, despite this short period of time, ‘In the Land Of Ultimate Bliss, those sentient beings born, are all Avaivartikas. Among them, many are in the Position Of One Life To Replacement, with their number extremely great, that cannot by counting their number be known of, and only can with immeasurable and boundless Asaṃkhyeya-[Kalpas be] said.’ (极乐国土，众生生者，皆是阿鞞跋致。其中多有一生补处，其数甚多，非是算数所能知之，但可以无量无边阿僧祇说。) What is inconceivable is that within just 10 Mahā-Kalpas, there are already countless beings in the Pure Land who are on the brink of Buddhahood. This bears testimony to the efficiency of the Pure Land in training beings towards Buddhahood.
Although the stages attainable in the Pure Land are in greater detail below, they should not be a key concern, as whatever stage one first realises, it will be non-retrogressible, and only lead to steady progression in spiritual practice. Due to the supremely blessed environment of the Pure Land, it is not necessary to ascend all the 52 stages to Buddhahood one by one in a slow and gradual way. As such, the Pure Land offers the most accelerated and thus swiftest path towards Buddhahood.
[Note: The time conversion below is based on this teaching by Śākyamuni Buddha (释迦牟尼佛) in the Flower Adornment Sūtra’s Thus Come Ones’ Lifespans’ Chapter《华严经·如来寿量品》, ‘This Sahā World’s Śākyamuni Buddha’s land’s one kalpa, is of the Land Of Ultimate Bliss, Amitā[bha] Buddha’s land, as one day and one night.’ (此娑婆世界释迦牟尼佛刹一劫，于极乐世界阿弥陀佛刹为一日一夜。) In short, 1 Mahākalpa in the human realm here is equivalent to 1 day and 1 night (e.g. 24 hours) in Āmítuófó’s Pure Land.]
The Contemplation Sūtra《观经》states that beings of  the Low Grade’s Low Birth (下品下生) [who have done the Five Heinous Transgressions (五逆罪) and the Ten Evil Karmas Deeds (十恶业), who repent (忏悔) and practise (行) mindfulness of Buddha with profound faith (信) and sincere aspiration (愿) for birth in Pure Land] will be reborn from lotuses after 12 Mahā-Kalpas here (in terms of human time, which is only 12 days and 12 nights there), and give rise to the irreversible Bodhi Mind (i.e. Bodhicitta [菩提心], the aspiration to seek Buddhahood for oneself and to guide all others to it too). This is in sharp contrast with being reborn in Avīci Hell (阿鼻地狱) to suffer relentlessly for an unimaginably longer duration, with an uncertain limit, thereafter being reborn gradually in better lives to ‘restart’ spiritual cultivation. Due to Āmítuófó’s bountiful merits, which he is ready to share, mindfulness of Buddha is the only way to escape from otherwise certain fall into the hells.
 The Low Grade’s Middle Birth (下品中生) requires 6 Mahā-Kalpas here (which is 6 days there) to be born, to soon give rise to the Bodhi Mind.
 The Low Grade’s High Birth (下品上生) requires only 49 days here (which is 0.000003452464512 of 1 minute there) to be born, and 10 Small Kalpas (小劫) (167,980,000 years here, which is 3 hours there) to realise the First Ground (初地) Of Bodhisattvahood (菩萨果). If we are sincere and proficient Dharma practitioners, we are likely to be born in higher grades of births, thus taking even less time to realise Buddhahood.
For  the Middle Grade’s Low Birth (中品下生), one realises as a Srotāpanna (须陀洹) after 7 days of birth here (which is 0.000000020550384 of 1 minute there) and as an Arhat (阿罗汉) after 1 Small Kalpa (16,798,000 years here, which is 18 minutes there).
For  the Middle Grade’s Middle Birth (中品中生), one realises as a Srotāpanna after 7 days of birth here (which is 0.000000020550384 of 1 minute there) and as an Arhat after half of 1 Small Kalpa here (which is 9 minutes there).
For  the Middle Grade’s High Birth (中品上生), one realises as an Arhat almost immediately when born soon (which is between ‘1 day and 1 night’ to ‘7 days’ here, between 0.000000002935728 and 0.000000020550384 of 1 minute there).
For  the High Grade’s Low Birth (上品下生), one is born from a lotus after 1 day and 1 night here (which is 0.000000002935728 of 1 minute there), and able to realise the Stage Of First Ground (初地) Of Joy (喜地) after 3 Small Kalpas here (which is 54 minutes there).
For  the High Grade’s Middle Birth (上品中生), one will be born after 1 night here (which is 0.000000001467864 of 1 minute there), and able to realise the Stage Of Eighth Ground (八地) Of Immovability (不动地) after 7 days here (which is 0.000000020550384 of 1 minute there) and realise Non-Arising Of Dharmas’ Forbearance (无生法忍) after 1 Small Kalpa here (which is 18 minutes there).
For  the High Grade’s High Birth (上品上生), one will realise Non-Arising Of Dharmas’ Forbearance (which is equivalent to the Eighth Ground) upon (instant) birth (as there is no mention of a lotus ‘incubation’ period), swiftly becoming a Dharma Body’s Bodhisattva Mahāsattva (法身大士). Even Great Bodhisattvas (大菩萨) who have realised Equal Awakening (等觉) like Universal Virtue (普贤) and Mañjuśrī (文殊) express the need to practise mindfulness of Buddha, by aspiring to be born in Āmítuófó’s Pure Land – because the path to Buddhahood there is incredibly swift and cannot be compared with other worlds.
All beings who reach the Pure Land are Avaivartikas (阿鞞跋致) because they are non-retrogressible (不退转) in three ways (三不退) – in terms of Position (位不退: never backsliding to rebirths in the lower realms, and are bound for at least Arhathood), Practice (行不退: never backsliding to goals lesser than Buddhahood), and Mindfulness (念不退: never backsliding from moment-to-moment mindfulness of awakening, and is aligned in every thought with the deep and vast ocean of the Buddhas’ wisdom). A remarkable aspect of being born in Pure Land is that although one might not have technically realised non-retrogression in all three ways immediately when it is reached, one is nevertheless on the non-retrogressible path of realising them there fully.
From the above, we can note that beings who can be born in the Pure Land are unlimited in nature. They range from those who had done great evil, to those who are average, to those who are not even Srotāpannas yet, to those who are good Dharma practitioners, to those on the brink of Buddhahood (e.g. Great Bodhisattvas who have realised Equal Awakening – who can reach there instantly via mindfulness; not via lotus births). As taught in the Contemplation Sūtra, the first attainment one realises in the Pure Land depends on one’s prior diligence in Dharma practice. They range from Srotāpannahood to Arhathood, from giving rise to irreversible Bodhi Mind to realising the First Ground (up to the Eighth Ground). All these will lead up to Equal Awakening, and Wonderful Awakening after ‘graduation’ from the Pure Land. While staying in Saṃsāra even for a long time tends to lead to little progress towards Buddhahood, with mindfulness of Buddha, the aspiration for Buddhahood will no longer be a distant dream for everyone!
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