How are the Seven Links to Awakening
Fulfilled?

Once in
Savatthi
the Blessed
Buddha said this:
How,
Ānanda, are the
Four Foundations of Awareness trained and developed
so
that they fulfil the
Seven Links to Awakening?
Whenever,
Ānanda, a Bhikkhu is reflecting
upon the body only as an accumulation,
right on that very occasion, unconfused and undistracted awareness is established
in that Bhikkhu. Therefore on that occasion the
Awareness Link to Awakening is
aroused, and as it gradually develops, it
reaches a fine fulfilment in that Bhikkhu.
Dwelling thus aware, he investigates
and examines that state by understanding.
Whenever,
Ānanda, a Bhikkhu dwells
investigating any state, on that occasion the
Investigation Link to Awakening is aroused,
and as it gradually develops by many
repetitions,
it reaches fulfilment in that Bhikkhu. While he
investigates phenomena
using keen intelligence, examines them, his energy is aroused without slackening!
On that occasion the
Energy Link to Awakening is enlivened,
and as it gradually
develops by many
reiterations, it comes to reach fine fulfilment in that Bhikkhu.
When his
enthusiastic energy is aroused, there arises in him
a rapturous joy :-)
On that occasion the
Joy Link to Awakening is instigated,
and as it gradually
develops by many
renewals, it comes to reach fine fulfilment in that Bhikkhu.
Both the body and mind
becomes tranquil, in whoever is mentally
elated by joy.
On that occasion the
Tranquillity Link to Awakening is therefore induced, and
as it gradually
develops by maturation, it reaches fulfilment in that Bhikkhu.
In one whose body is tranquil,
and who is happy, the mind becomes concentrated!
On that occasion, the
Concentration Link to Awakening is therefore stimulated,
and
as it gradually
develops by training, it reaches fine fulfilment in that Bhikkhu.
He then just looks on this concentrated mind with imperturbable
equanimity...
On that occasion is therefore induced the
Equanimity Link to Awakening, and
as it gradually
develops by rehearsal, it reaches fulfilment in that Bhikkhu.
It is,
Ānanda, when the four
Foundations of Awareness are trained
and refined
in exactly this very way, that they fulfill the
Seven Links to Awakening...!

More on these Seven Sublime Links to Awakening:
https://What-Buddha-Said.net/drops/III/The_Seven_Links_to_Awakening.htm
https://What-Buddha-Said.net/drops/III/Awareness_Sati.htm
https://What-Buddha-Said.net/drops/III/Investigation_Vicaya.htm
https://What-Buddha-Said.net/drops/III/Energy_Viriya.htm
https://What-Buddha-Said.net/drops/III/Joy_Piti.htm
https://What-Buddha-Said.net/drops/III/Tranquillity_Passaddhi.htm
https://What-Buddha-Said.net/drops/III/Concentration_Samadhi.htm
https://What-Buddha-Said.net/drops/III/Equanimity_Upekkha.htm

Source
(edited extract):
The
Grouped Sayings of the Buddha. Samyutta
Nikāya. [V:331-33]
section 54: Ānāpānasamyutta.
Thread 13: Ānanda