To anyone who approaches it in a hasy manner this passage will seem difficult and something of a trap with regard to the faith. Consequently, at this juncture there are already those who expect us to get bogged down in insuperable difficulties thrown up by our opponents. But there is nothing at all difficult here. ‘For all things are straightforward to those who understand,’ as Scripture says, ‘and plain to those who fine knowledge’ (Pov. 8:9), that is to those who devoutly study to interpret and understand the mysteries contained in the divine Scriptures.
~Cyril of Alexandria Commentary on John 4.1