Śrāddha-kalpa: Dāna-phala-nirdeśa
Gifts in Śrāddha and Their Fruits
यज्ञोपवीतं यो दद्याच्छ्राद्धकाले तु यज्ञवित् / पावनं सर्व विप्राणां ब्रह्मदानस्य तत्फलम्
yajñopavītaṃ yo dadyācchrāddhakāle tu yajñavit / pāvanaṃ sarva viprāṇāṃ brahmadānasya tatphalam
One who knows the yajña, if at the time of śrāddha he gives the yajñopavīta (sacred thread) in charity, thereby purifies all vipras; such is the fruit of brahma-dāna.