Manu Samoa posted on their Facebook page a video of the team singing the hymn Fa'afetai i le atua (Thank you, God, our Creator) sung in Brighton, England.
The video shows the players dressed in blue training gear standing and singing to van der Westhuizen who sits in a wheelchair dressed in a Springboks hoodie.
Van der Westhuizen was diagnosed with motor neurone disease in 2011 and given between two and five years to live.
The hymn is well-known in the Samoan community. The chorus says: "Sing hallelujah, thank you, hallelujah".