Elon Musk sold 4.4 million shares of $Tesla(TSLA.US)$. The total value was $3.99 billion, according to five Form 4 filings.
Musk needs $21 billion in cash for his Twitter takeover bid, which could mean selling some of his Tesla stock holdings, to close the deal.
On Twitter, he claimed "No further TSLA sales planned after today".
SEC Filings
https://www.sec.gov/Archives/edgar/data/0001318605/000089924322015924/xslF345X03/doc4.xml
https://www.sec.gov/Archives/edgar/data/0001318605/000089924322015923/xslF345X03/doc4.xml
https://www.sec.gov/Archives/edgar/data/0001318605/000089924322015942/xslF345X03/doc4.xml
https://www.sec.gov/Archives/edgar/data/0001318605/000089924322015949/xslF345X03/doc4.xml
https://www.sec.gov/Archives/edgar/data/0001318605/000089924322015955/xslF345X03/doc4.xml