exiftool  -q -r -ext jpg -if '
     $ImageWidth > 1000 ||
     $ImageHeight > 1000 and
       !print "$Directory/$Filename"' . |
   xargs -r0 sh -c '
     for file do
       mv -i "$file" "$file.bak" &&
         convert -resize "1000x1000>" "$file.bak" "$file" &&
         touch -r "$file.back" "$file"
     done' sh