There are two things conducive to knowledge. 
(1) Tranquility and
(2) discernment. 
What is the purpose of undertaking the development of Tranquility? 
The mind comes to be developed.
What is the purpose of developing the mind?
One’s tension  comes to be abandoned.
What is the purpose of developing discernment? 
Wisdom comes to be developed.
What is the purpose of developing wisdom?
One’s lack of awareness comes to be abandoned.
“Soiled by greed bhikkhus,
The mind is not released,
Soiled by ignorance,
Wisdom is not developed.
By the undoing of craving,
There is mind-release.
By the undoing of ignorance,
There is wisdom-release.” 
 “Dve me, bhikkhave, dhammā vijjābhāgiyā.
 These two are always ‘yoked’ together. See MN 149 Mahāsaḷāyatanika Sutta: “Tassime dve dhammā yuganandhā vattanti— samatho ca vipassanā ca.”
Samatha: A term which I sometime translate as “Letting go” to better represent its true function as a more active principle. Pāḷi is a very neutral and passive language which tends to be translated as such in English also but this does not always facilitate the proper understanding to English practitioners. Here the term samatha is the ‘active’ component whereby unwholesome states and tension are released, relaxed and given up to give rise to clarity (vipassanā), which is then used again to see ever more subtle, deeper rooted unwholesome inclinations and tension in the mind.
 Samatho, bhikkhave, bhāvito kamatthamanubhoti? Cittaṁ bhāvīyati. Cittaṁ bhāvitaṁ kamatthamanubhoti? Yo rāgo so pahīyati. Craving. This means, longing for sensory stimulation at any of the senses, which needs to be abandoned at the first jhāna (vivicc’eva kāmehi). Cultivating the higher mind is equated to the practice of meditation (jhāna) as in AN III 89 Paṭhamasikkhattaya Sutta. https://www.heartdhamma.love/sutta/an-iii-89/
 This is one of the exceedingly rare occasions where the Buddha himself does venture to tell us a little bit more about what is meant by this famous combination of samatha and vipassana which is often rendered as “tranquility and insight.” Although this translation has gotten wide-spread and almost categorical, it is not necessarily the most accurate. Some uses of the word “vipassanā” which comes from the verb ‘vipassati’ and means ‘to see clearly’ seem to deliver a different perspective on the term. See in AN VII 15 Udakūpama Sutta. The word “insight’ itself has become loaded with various interpretations from a colorful spectrum of sources, like the word ‘awakening’ or ‘enlightenment’ which have now become notions contaminated by opinions and beliefs having little to do with the original teaching of the Buddha. The modern outlook on samatha-vipassanā practice derives from a very popular book called the Visuddhimagga, written roughly around the 5th century CE in Sri Lanka, that is more than a thousand years after the Buddha’s passing. This is where we can trace what seems to be the first person who ventures on a great elaboration on the two (Samatha-vipassanā), divising them into two separate practices. The suttas seem to suggest a different story where the two would always be practiced together, inseparably yoked. Interestingly, no sutta can be found where the Buddha himself would support their separation as two different practices, even less describing what they are.
Rāgupakkiliṭṭhaṁ vā, bhikkhave, cittaṁ na vimuccati, avijjupakkiliṭṭhā vā paññā na bhāvīyati. Iti kho, bhikkhave, rāgavirāgā cetovimutti, avijjāvirāgā paññāvimuttī”ti.