तीर्थवंशोपदेशः
Tīrtha-vaṃśa Upadeśa: Instruction on the Fruits of Sacred Waters
भीष्म उवाच दैवं पौर्वाह्निकं कुर्यादपराह्ने तु पैतृकम् मड़लाचारसम्पन्न: कृतशौच: प्रयत्नवान्
bhīṣma uvāca: daivaṃ paurvāhṇikaṃ kuryād aparāhṇe tu paitṛkam | maṅgalācāra-sampannaḥ kṛtaśaucaḥ prayatnavān ||
Bhishma said: “One should perform the rites and gifts meant for the gods in the forenoon, and those meant for the ancestors in the afternoon. Having completed purification (such as bathing) and being endowed with auspicious observances, one should act with diligence. A gift made at an improper time is regarded as the share of the rākṣasas.”
भीष्म उवाच
Perform divine offerings in the forenoon and ancestral offerings in the afternoon, with ritual purity and auspicious conduct; right timing and cleanliness are integral to dharma and to the proper fruit of giving.
In Bhishma’s instruction on dharma (Anushasana Parva), he lays down a practical rule about when to perform different categories of rites/charity—distinguishing obligations to gods and to ancestors—and stresses purification and disciplined effort.