Aśauca-vidhi (Rules of Impurity) within Śrāddha-kalpa — Chapter on Testing/Selecting Brahmanas and Honoring the Atithi
आश्रमो ऽपावनो यस्तु पञ्चमस्संकरात्मकः / चत्वारस्त्वाश्रमाः पूच्याः श्राद्धे देवे तथैव च
āśramo 'pāvano yastu pañcamassaṃkarātmakaḥ / catvārastvāśramāḥ pūcyāḥ śrāddhe deve tathaiva ca
The fifth āśrama, of mixed and confused nature, is impure; in śrāddha and in worship of the gods, only the four āśramas are to be revered.