'Three Days' in the Bible

Then said the king to Amasa, Assemble me the men of Judah within three days, and you be here present.

So Gad came to David, and told him, and said unto him, Shall seven years of famine come unto you in your land? or will you flee three months before your enemies, while they pursue you? or shall there be three days' pestilence in your land? now consider, and see what answer I shall return to him that sent me.