Ivanka Trump surprised many of her followers on Instagram when she sent out a famous rabbinic aphorism but attributed it to Harry Potter star Emma Watson.

She uploaded an image which said, “If not me, who? If not now, when?” and attributed it to Watson, most famous for playing Hermione Granger in the Harry Potter series.

The original version of the so-called Watson quotation appears in Pirkei Avot (the Ethics of the Fathers), and is said by venerated first century Rabbi Hillel the Elder.

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It reads, “If I am not for myself, who will be for me? But if I am only for myself, what am I?”

Although it is likely that Ivanka does not manage her own Instagram account, many people on Twitter found it ironic that despite her Orthodox Jewish conversion in 2009, the daughter of Republican presidential nominee Donald Trump chose not to quote the original source of this saying.

Emma Watson in her 2014 HeForShe UN Speech #ITwisewords #WiseWords #Quotes @emmawatson A post shared by Ivanka Trump (@ivankatrump) on Sep 9, 2016 at 11:03am PDT

Watson did in fact say those words, in a 2014 speech to the United Nations about gender equality. Watson did not cite the source of her words.

“In my nervousness for this speech and in my moments of doubt I’ve told myself firmly — if not me, who, if not now, when,” she said. “If you have similar doubts when opportunities are presented to you I hope those words might be helpful.”

Twitter was quickly filled with tweets poking fun at Ivanka and her failure to correctly credit the rabbi who first made this statement. Alluding to the “Hillel sandwich” eaten on Passover seder night, one person wrote, “And every passover, we eat the Emma Watson sandwich.”

And every passover, we eat the Emma Watson sandwich https://t.co/pENUzrZv7F — Kiera Feldman (@kierafeldman) September 9, 2016

Hillel’s teaching has quoted by many US politicians in the past, without attribution.

In a 1981 speech, US President Ronald Reagan said, “We have to ask ourselves if we do nothing, where does all of this end. Can anyone here say that if we can’t do it, someone down the road can do it, and if no one does it, what happens to the country? All of us know the economy would face an eventual collapse. I know it’s a hell of a challenge, but ask yourselves if not us, who, if not now, when?”

Reagan was cited as the originator of this statement in 2012 by Virginia governor Bob McDonnell who told the Republican Party platform committee, “We must answer Ronald Reagan’s question: If not us, who? And if not now, when?”

Even President Barack Obama quoted the mishna, again without attribution. “My question to them is: When is the right time? If not now, when? If not us, who?” he told Congress in 2010.

In fact, Obama has used the quote in conversation with Prime Minister Benjamin Netanyahu. He told Jeffrey Goldberg that every time he meets Netanyahu, “the essence of my conversation,” is this: “If not now, when? And if not you, Mr. Prime Minister, then who? How does this get resolved?”

Netanyahu has also used the quote defending his opposition to Obama’s handling of Syria and Iran. “If I am not for myself, who will be for me?” Netanyahu told a Israeli Navy graduation ceremony in 2013. He said this rule “is more relevant than ever these days in guiding me, in my key actions as prime minister.”

The quote has also been attributed to John F. Kennedy.