MN 36 4th jhāna and samādhi all the time in all postures, when mind is not engaged in thinking and giving Dhamma talks

excerpt from MN 36

(eat some food for enough energy to do 4 jhanas)

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(with imperturbable 4th jhana samadhi, reach 3 higher knowledges)

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(samadhi that is jhāna quality after giving dhamma talk)

Abhijānāmi kho panāhaṃ, aggivessana, anekasatāya parisāya dhammaṃ desetā.	Aggivessana, I recall teaching the Dhamma to an assembly of many hundreds,
Apissu maṃ ekameko evaṃ maññati:	and each person thinks
‘mamevārabbha samaṇo gotamo dhammaṃ desetī’ti.	that I am teaching the Dhamma especially for them.
Na kho panetaṃ, aggivessana, evaṃ daṭṭhabbaṃ;	But it should not be seen like this.
yāvadeva viññāpanatthāya tathāgato paresaṃ dhammaṃ deseti.	The Realized One teaches others only so that they can understand.
So kho ahaṃ, aggivessana, tassāyeva kathāya pariyosāne, tasmiṃyeva purimasmiṃ samādhinimitte ajjhattameva cittaṃ saṇṭhapemi sannisādemi ekodiṃ karomi samādahāmi, yena sudaṃ niccakappaṃ viharāmī”ti.	When that talk is finished, I still, settle, unify, and undistractify-&-lucidify my mind in samādhi internally, using the same meditation subject as a basis of undistractible-lucidity that I used before, which is my usual meditation.”