Mbh 13.23.2a

"'Bhishma said, "Having purified oneself (by baths and other purificatory acts) and then going through the well-known auspicious rites, one should carefully do all acts relating to the deities in the forenoon, and all acts relating to the Pitris in the afternoon. What is given to men should be given in the midday with affection and regard. That gift which is made untimely is appropriated by Rakshasas.[211] Gifts of articles that have been leapt over by any one, or been licked or sucked, that are not given peacefully, that have been seen by women that are impure in consequence of their season having come, do not produce any merit. Such gifts are regarded as the portion belonging to the Rakshasas. Gifts of articles that have been proclaimed before many people or from which a portion has been eaten by a Sudra, or that have been seen or licked by a dog, form portions of Rakshasas. Food which is mixed with hair or in which there are worms, or which has been stained with spittle or saliva or which has been gazed at by a dog or into which tear-drops have fallen or which has been trodden upon should be known as forming the portion of Rakshasas. Food that has been eaten by a person incompetent to utter the syllable Om, or that has been eaten by a person bearing arms, O Bharata, or that has been eaten by a wicked person should be known to form the portion of Rakshasas.[212] The food that is eaten by a person from which a portion has already been eaten by another, or which is eaten without a part thereof having been offered to deities and guests and children, is appropriated by Rakshasas. Such stained food, if offered to the deities and Pitris is never accepted by them but is appropriated by Rakshasas. The food offered by the three regenerate classes in Sraddhas, in which Mantras are either not uttered or uttered incorrectly and in which the ordinances laid down in the scriptures are not complied with, if distributed to guests and other people, is appropriated by Rakshasas.