Bhagavad Gita 17.20
The gift that is given without thought of recompense, believing it should be made, in an appropriate place, at an opportune time, and to a deserving person—such a gift is pure.
दातव्यमिति यद्दानं दीयतेऽनुपकारिणे।देशे काले च पात्रे च तद्दानं सात्त्विकं स्मृतम्॥dātavyamiti yaddānaṃ dīyate'nupakāriṇe|deśe kāle ca pātre ca taddānaṃ sāttvikaṃ smṛtam||
English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).