SN 35.200 Dārukkhandha Sutta: The Log
The Buddha points out a big log floating down the Ganges. He says it will definitely reach the sea if it doesn’t get snagged up or sinks. If people follow the path, don’t get snagged and don’t sink they will definitely reach enlightenment.
The ‘snagging’ and ‘sinking’ refers to becoming attached to the senses and doing evil things.