Purusha sukta (in a verse considered by modern scholars to be a later interpolation) implies it ( "The Brahmana was his mouth; the Rajanya (Kshatriya) was made his arms; the Vaishya was his thighs; and the Sudra made his feet").
But does it say explicitly anywhere that one caste has higher status or rank than another? In particular, anything about the relative ranks of Brahmins and kshatriyas?
Yes they do say.. The concept of superiority and inferiority among Varnas is definitely there in the scriptures.
Manu Smriti 9.335. (A Sudra who is) pure, the servant of his betters, gentle in his speech, and free from pride, and always seeks a refuge with Brahmanas, attains (in his next life) a higher caste.
Here, in the Sanskrit original, for higher caste, UtkrishtAm jAtim is used and Utrkrishta means superior.
Similarly, see the following verse:
Manu Smriti 5.163. She who cohabits with a man of higher caste, forsaking her own husband who belongs to a lower one, will become contemptible in this world, and is called a remarried woman (parapurva).
Here, the original verse has "Patnim hitvA upakrishtam svam utkrishtam yA nishevate |"
So, the concept of higher and lower Varnas is definitely there in scriptures.
And, obviously, the BrAhmins are regarded as the most superior and the Shudras the most inferior among the four.
BrAhmin's superiority is established thus:
Manu Smriti 10.3. On account of his pre-eminence, on account of the superiority of his origin, on account of his observance of (particular) restrictive rules, and on account of his particular sanctification the Brahmana is the lord of (all) castes (varna).
and,
1.96. Of created beings the most excellent are said to be those which are animated; of the animated, those which subsist by intelligence; of the intelligent, mankind; and of men, the Brahmanas;
1.97. Of Brahmanas, those learned (in the Veda); of the learned, those who recognise (the necessity and the manner of performing the prescribed duties); of those who possess this knowledge, those who perform them; of the performers, those who know the Brahman.
Now, among the first two Varnas, relative superiority is established thus:
2.135. Know that a Brahmana of ten years and Kshatriya of a hundred years stand to each other in the relation of father and son; but between those two the Brahmana is the father.
Now, as you already know what the Purusha Sukta says about the origins of the four castes from various portions of it's body.
And, the following verse says, that because the Vaishyas and Shudras were created from the thighs and feet respectively, they are to be considered as less pure than the other two.
1.92. Man (Purusha is the word in the original) is stated to be purer above the navel (than below); hence the Self-existent (Svayambhu) has declared the purest (part) of him (to be) his mouth.
The logic is, since the Brahmins came out of the purest part, they are the purest among the Varnas and so on.
I have found some of the verses ,which you are looking from Shreemad Bhagvat Purana .
It is said in above shlokas that Brahmin Varna is foremost among the varnas. Also among Brahmanas who recite the vedas is superior , among the reciter of the vedas those who understand the meaning of the Vedas are more superior and among those ,who solve the doubts and difficulties is superior. those Brahmanas are more superior among rest of the previous ones who follow their Varnashrama Dharma well . But among all the Brahmanas highest are those who renounced all association and does not desire the fruit of his religious acts .
मुखतोऽवर्तत ब्रह्म पुरुषस्य कुरूद्वह ।
यस्तून्मुखत्वाद्वर्णानां मुख्योऽभूद्ब्राह्मणो गुरुः ॥SB 3.6.30॥mukhato 'vartata brahma puruṣasya kurūdvaha | yas tūnmukhatvād varṇānāḿ mukhyo 'bhūd brāhmaṇo guruḥ ||
O leader of Kurus ! From the mouth of the Purusha came forth Brahman (the veda) and the Brahmana class like syllables coming out from the mouth (head) . Hence the Brahmana Varna became the foremost amaong the Varnas.
ततो वर्णाश्च चत्वारस्तेषां ब्राह्मण उत्तमः ।
ब्राह्मणेष्वपि वेदज्ञो ह्यर्थज्ञोऽभ्यधिकस्ततः ॥SB 3.29.31॥tato varṇāś ca catvāras teṣāḿ brāhmaṇa uttamaḥ
brāhmaṇeṣv api veda-jño hy artha-jño 'bhyadhikas tataḥAmong the bipeds , four Varnas are superior and the Brahmanas are the higest among them. Among the Brahmanas ,the reciters of Vedas are higher. Superior to these are those who understand the meaning of the Vedas.
अर्थज्ञात्संशयच्छेत्ता ततः श्रेयान्स्वकर्मकृत् ।
मुक्तसङ्गस्ततो भूयानदोग्धा धर्ममात्मनः ॥SB 3.29.32॥artha-jñāt saḿśaya-cchettā tataḥ śreyān sva-karma-kṛt
mukta-sańgas tato bhūyān adogdhā dharmam ātmanaḥHe who can solve doubts and difficulties (of vedic interpretation) is superior to him who simply knows the meaning of the veda. To him is superior the performer of one's prescribed religious duties. But a person who has renounced all association and does not desire the fruit of his religious acts is higher than previous one.
