I agree that this concise summary: "the 4 sp fulfill the 7 sb and culminate in the 4 jhānas" packs the whole of the Buddha's teachings into one sentence and could benefit from some unpacking with sutta references.
Thanks to budo for his comments and solid sutta references to back them up. In the spirit of fidelity to the suttas, I would rephrase his statement that
"There is only one path, jhanas & contemplation of dhamma", to
"there is only the middle path that the buddha awakened to, namely ariyan right samādhi supported by ariyan right view… ariyan right mindfulness, which gives rise to vision, which gives rise to knowledge, which leads to peace, to direct knowledge, to awakening, to Nibbāna" (See the Buddha's first discourse SN 56.11).
Ariyan right samādhi is defined in the suttas as the one-pointedness of mind that is produced by ariyan right view… ariyan right mindfulness as its bases and requisites (see DN 18) or the four jhānas (see SN 45.8). So one who attains the 4 jhānas without ariyan right view is praised for attaining wholesome dhammas and superhuman states in knowledge and vision worthy of the ariyas, but is blamed for missing the ariyan 8-fold path which leads to Nibbāna (see SN 42.12). Ariyan right view is the deciding factor.
On the subject of unpacking the concise summary that "the 4 sp fulfill the 7 sb and culminate in the 4 jhānas", here are the sutta references:
MN 44 : Cūḷavedallasutta (4 sp are samādhinimittā)
“one-pointedness of mind is samadhi;
ekaggatā ayaṃ samādhi;
the four foundations of mindfulness are the sign of samadhi (samādhinimittā);
cattāro satipaṭṭhānā samādhinimittā;
the four right kinds of striving are the requisites of samadhi;
cattāro sammappadhānā samādhiparikkhārā.
the pursuit, keeping-in-being (guarding, retaining, keeping alive), and making-abundant (repetition, increasing) of these same dhammas is the keeping-in-being of samadhi therein.”
Yā tesaṃyeva dhammānaṃ āsevanā bhāvanā bahulīkammaṃ, ayaṃ ettha samādhibhāvanā”ti.
DN 28. Serene faith
In just the same way, it seems to me, Bhante, is the drift of the Dhamma.
Evameva kho me, bhante, dhammanvayo vidito.
For, Bhante, all those Arahant Buddhas of the past, having abandoned the five hindrances, defilements of mind that weaken wisdom, with their minds firmly established the four foundations of mindfulness, having developed the seven factors of awakening as they have come to be, attained to supreme awakening.
Ye te, bhante, ahesuṃ atītamaddhānaṃ arahanto sammāsambuddhā, sabbe te bhagavanto pañca nīvaraṇe pahāya cetaso upakkilese paññāya dubbalīkaraṇe catūsu satipaṭṭhānesu suppatiṭṭhitacittā, satta sambojjhaṅge yathābhūtaṃ bhāvetvā anuttaraṃ sammāsambodhiṃ abhisambujjhiṃsu.
What does it mean to have one's mind firmly established in the four foundations of mindfulness?
SN 22.80 alms gatherer
“There are, bhikkhus, these three kinds of unwholesome thoughts: sensual thought, thought of ill will, thought of harming.
Tayome, bhikkhave, akusalavitakkā— kāmavitakko, byāpādavitakko,vihiṃsāvitakko.
And where, bhikkhus, do these three unwholesome thoughts cease without remainder?
Ime ca bhikkhave, tayo akusalavitakkā kvaaparisesā nirujjhanti?
For one who dwells with a mind firmly established in the four establishments of mindfulness, or for one who develops the signless concentration.
Catūsu vā satipaṭṭhānesu suppatiṭṭhita cittassa viharato animittaṃ vāsamādhiṃ bhāvayato.
This is reason enough, bhikkhus, to develop the signless concentration.
Yāvañcidaṃ, bhikkhave, alameva animittosamādhi bhāvetuṃ.
MN 78. With Uggāhamāna Samaṇamuṇḍika - Samaṇamuṇḍikasutta
“What are unwholesome intentions?
Katame ca, thapati, akusalā saṅkappā?
They are the intention of sensual desire, the intention of ill will, and the intention of cruelty. These are called unwholesome intentions.
Kāmasaṅkappo, byāpādasaṅkappo,vihiṃsāsaṅkappo— ime vuccanti, thapati, akusalā saṅkappā.
“And what do these unwholesome intentions originate from?
Ime ca, thapati, akusalā saṅkappākiṃsamuṭṭhānā?
Their origin is stated: they should be said to originate from perception.
Samuṭṭhānampi nesaṃ vuttaṃ. ‘Saññāsamuṭṭhānā’ tissa vacanīyaṃ.
What perception? For perception is multiple, varied, and of different aspects,
Katamā saññā? Saññāpi hi bahū anekavidhānānappakārakā.
There is perception of sensual desire, perception of ill will, and perception of cruelty. Unwholesome intentions originate from this.
Kāmasaññā, byāpādasaññā, vihiṃsāsaññā— itosamuṭṭhānā akusalā saṅkappā.
“And where do these unwholesome intentions cease without remainder?
Ime ca, thapati, akusalā saṅkappā kuhiṃaparisesā nirujjhanti?
Their cessation is stated: here, quite secluded from sensual pleasures, secluded from unwholesome dhammas, a bhikkhu enters upon and abides in the first jhana, which is accompanied by applied and sustained thought, with rapture and pleasure born of seclusion. It is here that unwholesome intentions cease without remainder.
Nirodhopi nesaṃ vutto: Idha, thapati, bhikkhu vivicceva kāmehi …pe … paṭhamaṃ jhānaṃ upasampajjaviharati;
Budo stated rightly and with solid sutta reference that:
"Furthermore 4th jhana is considered COMPLETE PURITY OF MINDFULNESS".
I would add that one attains unwavering mindfulness of the body in the first jhana, although that mindfulness is not yet purified due to the presence of vitakka, vicāra, pīti and sukha. The first jhana simile of the body being saturated by pīti and sukha like a bath powder saturated with water but not oozing, makes the unwavering mindfulness of the body while in the first jhāna abundantly clear enough.
In the second jhana, the mind is quietened by the absence of vitakka and vicāra (ariyan silence) and the unwavering mindfulness of the body becomes more purified but still not fully purified due to the presence of pīti and sukha.
In the third jhana, unwavering mindfulness of the body is still there due to sukha on the body but the mind has withdrawn from mental pleasure of pīti and attained equanimity. The Buddha describe this as an abiding in mindfulness and clear comprehension (sati sampajāna) and the ariyas praise one who abides thus as "He is equanimous, mindful, one who dwells happily". But utter purity of minfulness is still lacking due to the presence of sukha.
It is only in the fourth jhana where the mind and the body have become unified in upekkha that unwavering mindfulness of the body reaches utter purity due to equanimity.