Charles Ellicott Commentary 2 Samuel 24:13

"So Gad came to David, and told him, and said unto him, Shall seven years of famine come unto thee in thy land? or wilt thou flee three months before thy foes while they pursue thee? or shall there be three days` pestilence in thy land? now advise thee, and consider what answer I shall return to him that sent me." — 2 Samuel 24:13 (ASV)

Seven years. —In Chronicles “three years,” and the Septuagint also reads this here. This would be more in accordance with the “three” months and “three” days.