As regards Rishis having penances for wealth they always avoid all creatures both before and behind, as also all that is impure, while performing Shraddhas.
भूतानि चैव सर्वाणि अग्रतः पृष्ठतोऽपि वा। उच्छिष्टं वापि च्छिद्रेषु वर्जयन्ति तपोधनाः॥