-From Ven. Anālayo's Excursions into the Thought-World of the Pāli Discourses, page 244-245, Pariyatti: 2012Another significant indication related to the nature of absorption can also be gathered from the Upakkilesa-sutta. According to its account, before his awakening the Buddha had to make quite an effort in order to overcome a whole series of obstructions until he was able to attain the first absorption (MN III 157). This suggests the first absorption to be a state of mind reached only after prolonged practice and requiring considerable meditative expertise.
This impression is confirmed by turning to the cases of Anuruddha and Mahāmoggallāna. In the case of each of these two chief disciples the personal intervention of the Buddha was required for them to be able to attain and stabilize the first absorption (MN III 157 and SN IV 263). If Anuruddha and Mahāmoggallāna, who later on were reckoned as outstanding among the Buddha’s disciples for their concentrative abilities (AN I 23), had such difficulties, then it can safely be concluded that the first absorption stands for a level of concentration that requires considerable meditative training.
Elsewhere the discourses in fact indicate that during the first absorption it is impossible to speak (SN IV 217), and the hearing of sounds is an obstruction to its attainment (AN V 135). With the first absorption one has gone beyond Māra’s vision (MN I 159), having reached the end of the world of the senses (AN IV 430). These passages confirm that the first absorption is indeed a state during which the mind is “absorbed” in deep concentration.
Highly recommended book.