As at SN 45.179, AN 10.13, etc. They are “lower fetters” because they bind sentient beings to rebirth in lower planes.

Given that Māluṅkyaputta got the answer right, it is not clear why the Buddha adopted the reproving tone that he would normally use in response to a dangerously mistaken view (MN 22:6.1). The commentary explains that he had the view that fetters were only present when active, hence the Buddha’s simile to follow. Regardless, as compared to MN 63, Māluṅkyaputta is making progress, as he gives a serious answer to an important question and appears to no longer be on the verge of disrobing.

For other accounts of infant development in relation to defilements, see AN 10.99:6.2 and MN 38:26.1.

The opening clause is a unique addition to the standard jhāna formula. | In later texts, “seclusion from attachments” (upadhiviveka) signified arahantship (Mnd 14:10.1), but here it must have a less exalted sense. Perhaps it refers to leaving behind the material things to which one is attached (SN 1.2). | For “bodily discomfort”, see MN 127:16.7.

This shows the development of insight based directly on the absorption.

The final formless attainment is omitted as at MN 52:14.7.

“Released in heart“ and “released by wisdom” indicate an emphasis on either immersion or wisdom respectively.

The Buddha makes the same point at SN 48.13 and SN 48:16. For more on the “disparity of faculties”, see MN 66:14.6.