It's not a good idea, but not for the reason stated here.
The TOR client will establish a tunnel OVER the VPN to the entry node, so the VPN provider will only see this encrypted traffic. The VPN server cannot spy on you.
When you connect to TOR it carefully selects your circuit for diversity over the Internet between each hop (for example avoiding your entry and exit nodes not being on the same service provider). By using a VPN your opening the possibility for something to go wrong here.
The TOR client will establish a tunnel OVER the VPN to the entry node, so the VPN provider will only see this encrypted traffic. The VPN server cannot spy on you.
When you connect to TOR it carefully selects your circuit for diversity over the Internet between each hop (for example avoiding your entry and exit nodes not being on the same service provider). By using a VPN your opening the possibility for something to go wrong here.