Former Vice President Joe Biden has some words of advice for President Trump about his social media habits.

“I would literally stop tweeting and start focusing,” Biden said Thursday at an event at the University of Pennsylvania, CNN reports. “The words of a president matter. They have enormous, enormous, enormous, reverberating sounds around the world. Every time a U.S. president speaks and says something, leaders and people around the world try to dissect what he means because it matters so much to their security, threats they face, whatever it is.”

Biden also repeated a piece of advice he’d already given to the new president: “Grow up.”

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Write to Tessa Berenson at tessa.berenson@time.com.