The below is with reference to: Twenty-Fourth Chapter On Three Grades Of Rebirths (Of Immeasurable Life Sūtra)《无量寿经》 三辈往生第廿四三 at https://purelanders.com/2020/05/dajing24
Immeasurable Life Sūtra’s Twenty-Fourth Chapter’s Summary & Explanation
 All beings born in Āmítuófó’s (阿弥陀佛) Pure Land (净土) will abide in the Right Definite Assembly (正定聚) (that is bound for Buddhahood), as it is without those of the Evil Assembly (邪聚) and Indefinite Assembly (不定聚).
 All countless Buddhas everywhere highly praise Āmítuófó’s inconceivable majestic supernormal powers (威神) and meritorious virtues (功德).
 All beings who hear Āmítuófó’s name with the faithful (信心) and joyful (欢喜) mind, even if for one thought, sincerely dedicating (至心回向), aspiring to be born (愿生) in his land, will immediately attain birth there, to abide in non-retrogression (不退转). Only excluded are those with the Five Heinous Transgressions (五逆罪), who slander the right Dharma (诽谤正法), (who have yet to repent).
 All beings with the sincere mind, aspiring to be born in Āmítuófó’s Pure Land have these Three Grades (三辈), with these causes (因), conditions (缘) and effects (果).
[i] High Grade (上辈)
[a] Renounce the household life, relinquish (worldly) desires and become Śramanas (i.e. Buddhist monastics) (捨家弃欲而作沙门),
[b] Give rise to the Bodhi Mind (i.e. Bodhicitta) (发菩提心),
[c] Wholeheartedly focus on mindfulness of Immeasurable Life Buddha (i.e. Āmítuófó) (一向专念无量寿佛),
[d] Cultivate all meritorious virtues (修诸功德),
[e] Aspire to be born in that land (愿生彼国).
[a] When approaching life’s end, Immeasurable Life Buddha and many (Bodhisattvas) in a great assembly, will appear before these persons (临寿终时，无量寿佛，与诸大众，现其人前) (to guide and receive them to reach his Pure Land).
[a] Immediately following that Buddha for rebirth in his land, then from seven treasures’ flowers within, naturally manifesting birth, to abide in non-retrogression (即随彼佛往生其国，便于七宝华中，自然化生，住不退转),
[b] With wisdom, courageous and powerful, supernormal powers with ease (智慧勇猛，神通自在).
(Beings who desire to see Āmítuófó in this life should give rise to unsurpassable Bodhicitta, cultivate practices with meritorious virtues, and aspire to be born in his Pure Land.)
[ii] Middle Grade (中辈)
[a] Have the sincere mind, and aspire to be born in that land (至心愿生彼国).
[b] Although not able to practise by becoming Śramanas, to greatly cultivate meritorious virtues (虽不能行作沙门，大修功德),
[c] They should give rise to the unsurpassable Bodhi Mind (当发无上菩提心),
[d] Wholeheartedly focus on mindfulness of Immeasurable Life Buddha (一向专念无量寿佛),
[e] More or less cultivate good, uphold the Purification Precepts, erect stupas and images, offer food to Śramanas, hang banners, light lamps, scatter flowers and burn incense (多少修善，奉持斋戒，起立塔像，饭食沙门，悬缯然灯，散华烧香),
[f] With these dedicate, aspire to be born in that land (以此回向，愿生彼国).
[a] For these persons when approaching the end of life, Immeasurable Life Buddha will manifest his body, with bright lights and forms’ excellences, complete like the real Buddha, with many in a great assembly, appearing before these persons (其人临终，无量寿佛，化现其身，光明相好，具如真佛，与诸大众，现其人前).
[a] Immediately following the manifested Buddha, for rebirth in his land, to abide in non-retrogression (即随化佛往生其国，住不退转).
[b] Their meritorious virtues and wisdom are second to those of the High Grade. (功德智慧，次如上辈者也)
[iii] Low Grade (下辈)
[a] Have the sincere mind, and desire to be born in that land (至心欲生彼国).
[b] If not able to create many meritorious virtues, they should give rise to the unsurpassable Bodhi Mind (假使不能作诸功德，当发无上菩提之心),
[c] Wholeheartedly focus their minds, and even with ten thoughts mindful of Immeasurable Life Buddha (一向专意，乃至十念，念无量寿佛),
[d] Aspire to be born in his land (愿生其国).
[a] If hearing the profound Dharma, rejoicing with joyful faith, not giving rise to doubts and confusions (若闻深法，欢喜信乐，不生疑惑),
[b] And even with one thought mindful of that Buddha (乃至一念，念于彼佛),
[c] With the utmost sincere mind, aspiring to be born in his land (以至诚心，愿生其国).
The above two sets of causes from [a]–[d] and from [a]–[c] can apply to the same person or different persons. The key differences are that the second set does not mention the Bodhi Mind, while mentioning even one thought of mindfulness will do. The Three Provisions (三资粮) of Faith (信), Aspiration (愿) and Practice (行) are still present, as joyful faith (信乐), aspiring to be born in his land (愿生其国), and one thought (一念) respectively.
[a] These persons, when approaching the end of life, will dream of seeing that Buddha (此人临终，梦见彼佛),
[a] Also attaining rebirth (亦得往生).
[b] Their meritorious virtues and wisdom are second to those of the Middle Grade. (功德智慧，次如中辈者也)
 According to the Pure Land Tradition’s 9th Patriarch Great Master Ǒuyì (净土宗九祖蕅益大师) in his ‘Essential Explanation Of The Amitā(bha) Sūtra As Spoken By The Buddha’《佛说阿弥陀经要解》, ‘With profound (i.e. deep) Faith giving rise to the Aspiration [to be born in Āmítuófó’s Pure Land], this is unsurpassable Bodhi[citta]… The “Larger [Version Of The] Amitā(bha) Sūtra” (i.e. Immeasurable Life Sūtra《无量寿经》), is likewise with giving rise to the Bodhi Aspiration (i.e. Bodhicitta) as essential [in its section on the Three Grades (三辈) for birth in Pure Land], which is exactly with this, the same [in meaning]. (深信发愿，即无上菩提。… 大本《阿弥陀经》，亦以发菩提愿为要，正与此同。)
The Three Provisions & Three Minds In Āmítuófó’s Three Vows For Gathering Sentient Beings: How Are His 18th, 19th & 20th Vows Related?
Why Is Upholding Āmítuófó’s Name With Faith & Aspiration The Main Practice?
What Is Unsurpassable Bodhicitta For Pure Land Birth?
Is Bodhicitta A Must For Birth In Amituofo’s Pure Land?
Never Say Those Without Bodhicitta Cannot Be Reborn In Pure Land
Verses On Pure Land Bodhicitta
Why There Must Be Skilful Speak Of Pure Land Bodhicitta
How The Three Lowest Grades Have Bodhicitta Too
Is 2nd Patriarch’s Unsurpassable Path’s Mind 9th Patriarch’s Unsurpassable Bodhi Mind?
Relationship Of Special With Common Bodhicitta
Even With One Thought Attains Birth In Pure Land
The Contemplation Sūtra’s Nine Grades (In Tabulated Lists)
Rebirth In Pure Land’s Causes, Conditions And Effects In The Amitābha Sūtra And The Sūtra On Praises Of The Pure Land With Buddhas’ Protection And Reception
Summary Verses Of ‘Section On Perfect Penetration With Mindfulness Of Buddha’