Unless they have given permission, then this is a big NO.  Doing so is plagiarism. Not only can you get in trouble for it legally, but you can get in trouble with Google too. 

If it’s a very cool blog, you can re-write it so it’s significantly different (use a programme like CopyScape to check it’s different enough) and then publish it. But you cannot copy someone else’s blog, website copy or LinkedIn post.