This quote is found on many quotations sites and is commonly found on social media. Happily it’s a genuine quotation, although it’s missing the punch-line:
“Drop by drop is the water pot filled. Likewise, the wise man, gathering it little by little, fills himself with good.”
It’s from verse 122 of the Dhammapada.
No doubt however the implied meaning of the shortened quotation is clear to most people.
Here’s a graphic from RealBuddhaQuotes.com, in case you want to share it.