The father of a Muslim American soldier killed on duty in Iraq received huge cheers by Democrat supporters as he challenged Donald Trump to "read the US constitution".
Khizr Khan, standing beside his wife Ghazala, reached inside his jacket pocket and pulled out the small book to whoops of delight inside the Democratic National Convention hall.
He accused the Republican presidential nominee of sacrificing "nothing" and "smearing the character" of religious minorities across America.
Mr Khan's son, Army Captain Humayun Khan, died from a suicide bomb in 2004 at the age of 28.
Trump has repeatedly called for a ban on Muslims entering the US as part of his proposed counter-terrorism policy.
"If it was up to Donald Trump, (Humayun) never would have been in America," Khan told the convention in a speech endorsing Hillary Clinton's candidacy.
"Donald Trump consistently smears the character of Muslims. He disrespects other minorities, women, judges, even his own party leadership. He vows to build walls and ban us from this country."
He went on: "Donald Trump, you are asking Americans to trust you with our future. Let me ask you: Have you even read the US Constitution?"
With his pocket constitution in hand, he said: "I will gladly lend you my copy. In this document, look for the words liberty and equal protection of law."
Mr Khan's address was widely praised by Democrat supporters both inside and outside the convention hall, while media commentators attributed his speech to an increase in online voter interest.