Because out of his fulness we have all received – grace upon grace. (John 1:16)
Although in recent years I can only recall one occasion where I have ordered one, in my teenage years, I used to get excited about something in restaurants: bottomless drinks. It was a treat to have, in effect, a permanently full cup – even if it was less good for the internal organs!
This verse talks about the fulness of the Word. Again, such language of fulness (plērōma) appeared in Antiquity – particularly in connection with Gnosticism, which was developing in the first century, and was most pervasive in the second – so was somewhat subversive. Christ is defined by his fulness (cf. Colossians 1:19); there is nothing lacking or incomplete in Him; He is all-sufficient.
Yet, out of his fulness, Christ generously gives of himself: we have all received, and specifically what we receive is grace. Paradoxically, Christ empties himself so that we might be filled up; but Christ remains bottomless. Our posture is to be a simple one: receiving. Yet, this is harder than it sounds: we might want to earn God’s approval. It is right to want to live in a way that honours God, including doing good works, but we cannot “outgive” the giver.
More seriously, there are times where we are in the wrong; and it is on those occasions that we need to receive ‘grace upon grace’, to recognise our wrong, but receive the fulness of God’s love – an infinite source, like wave after wave hitting the shore. Such grace does not mean that we can simply do as we choose and presume upon grace at the end. As Dietrich Bonhoeffer famously said, that would be “cheap grace”. Christ’s love and grace is costly: Jesus had to give His life to defeat the powers of darkness. Yet, we are back to the paradox that it cost Him both everything and nothing at the same time because He is the fulness of God. He is bottomless.
 The eagle-eyed might notice that I have omitted John 1:15, ‘John witnessed about him and cried out, saying: “This is the one about whom I said: the one who comes after me, has surpassed me, because he has been before me.”’ In the most recent NIV translation it is bracketed, suggesting a degree of doubt that it belongs here – cf. John 1:30. Many commentators reasonably posit that it could be an interpolation or a parenthetical remark, allowing for the easier transition between John 1:14 and John 1:16 as above.