The Arduino's output pins are at 5V. Some wireless modules are not 5V tolerant. So, to protect them, you can use a voltage divider to drop the 5V to ~3.3V. These wireless modules use SPI, so there are these pins involved:
MOSI MISO Clock Cable Select Interrupt
Is the voltage divider only needed on the MOSI, Clock, and Cable Select? The interrupt and the MISO are outputs from the module to the Arduino. As long as I don't accidentally make these pins outputs on the sketch, I should be OK?