To download a Facebook video without any software in a mobile phone, you can use the following steps:

1. Open the Facebook app and find the video you want to download.
2. Tap the three dots in the top right corner of the video and select Copy Link.
3. Open a web browser on your phone and go to a Facebook video downloader website, such as FBDownloader or FBDown.
4. Paste the copied link into the input box on the website and click Download.
5. Select the video quality you want to download and tap Download.
6. The video will be downloaded to your phone’s gallery.