The meaning of an apparently useless offering

Actually, no one can give anything to the Supreme Personality of Godhead,
for He is full in everything. Sometimes we see a devotee offering Ganges
water to the Ganges. After taking his bath in the Ganges, a devotee takes a
palmful of water and offers it back to the Ganges. Actually, when one takes
a palmful of water from the Ganges, the Ganges does not lose anything, and
similarly if a devotee offers a palmful of water to the Ganges, the Ganges
does not increase in any way. But by such an offering, the devotee becomes
celebrated as a devotee of mother Ganges. Similarly, when we offer anything
with devotion and faith, what we offer does not belong to us, nor does it
enrich the opulence of the Supreme Personality of Godhead. But if one offers
whatever he has in his possession, he becomes a recognized devotee.
>>> Ref. VedaBase => SB 8.20.21