Laudator Temporis Acti

Isidore of Seville, Etymologiae 5.30.8 (tr. Priscilla Throop):

The heathens named the days from these seven stars, because they thought that they obtained some quality through them: spirit from the sun, body from the moon, cleverness and language from Mercury, sensual enjoyment from Venus, blood from Mars, moderation from Jupiter, moisture from Saturn. Such was the foolishness of the heathens, who contrived for themselves such ridiculous ideas.

proinde autem ex his septem stellis nomina dierum gentiles dederunt, eo quod per eosdem aliquid sibi effici existimarent, dicentes habere a Sole spiritum, a Luna corpus, a Mercurio ingenium et linguam, a Venere voluptatem, a Marte sanguinem, a Iove temperantiam, a Saturno humorem. talis quippe extitit gentilium stultitia, qui sibi finxerunt tam ridiculosa figmenta.

Cf. Servius on Vergil, Aeneid 11.51, who unlike Isidore keeps the chronological order of the days of the week:

ut dicunt physici, cum nasci coeperimus, sortimur a Sole spiritum, a Luna corpus, a Marte sanguinem, a Mercurio ingenium, a Iove honorum desiderium, a Venere cupiditates, a Saturno humorem.