Food enchanted by spells (SN 7.8)
See pages 96-97 of Piya Tan's essay:


  The Saṁyutta Commentary paraphrases the significance of the two verses, thus (as the Buddha’s
  arrière pensée):
  
  
    Though I have stood for such a long time waiting for alms, you would not give even a spoonful;
    but now that I have revealed all the Buddha-qualities to you as though spreading out sesamum
    seeds on a mat, you wish to give. This food has been gained, as it were, by singing a song
    (gāyanena gāyitvā). Therefore, as it has been ‘chanted over with verses’ (gāthā’bhigīta) it is not
    fit to be eaten by me. Since there is the Dharma (dhamme sati), out of respect for the Dharma,
    established in the Dharma, the Buddhas sustain their life. This is their rule of conduct, this is their
    way of livelihood (esā vutti aya ājīvo). Such food should be discarded and only what is properly
    gained should be eaten.” (SA 1:232; see Miln 228-232)
  
  
  The Critical Pali Dictionary defines abhigīta as “spoken over with mantras,” suggesting that the Buddha
  rejects the offering by the brahmin because he has chanted over it with the sacrificial hymns. However,
  Bodhi thinks that “it is doubtful that the Buddha would reject food for such a reason. Further, according
  to [SED], gāthā is not used with reference to the verses of the Vedas, and thus here the word likely refers
  to the Buddha’s own verses” (S:B 446 n446).
  To suggest that the Buddha rejected the brahmin’s offering simply because it has been chanted over
  with Vedic mantras would suggest that the Buddha is superstitious! The real reason has to do with right
  livelihood (sammā,ājīva).


His translation is a bit different from Ven. Sujato's, i.e.:


  Gāthā’bhigītaṁ me abhojaneyyaṁ
  The gatha-sung should not be partaken by me, 
  
  sampassataṁ brāhmaṇa n’esa dhammo
  O brahmin, this is not the way of those who see.  
  
  gāthā’bhigītaṁ panudanti buddhā
  Buddhas reject what is gained by the singing of verses,
  
  dhamme sati brāhmaṇa vuttir esā.
  When there’s Dharma, brahmin, this is the rule.




I re-read the "food" chapters of these Vinaya summaries ...


The Bhikkhus' Rules --
A Guide for Laypeople
The Patimokkha Rules
The Khandhaka Rules


... and didn't see anything there about ex-sacrificial food not being allowable as alms food.