The sad truth is that, naturally, human beings do not love God - the person who made them, sustains them, provides for them and heaps goodness upon them.  We are all sinful from birth (Psalm 51:5): that is, we resist the authority of God and express that rebellion in a million different ways which the Bible calls 'sins'.  It is not that we have wandered from perfection: we start in imperfection and daily deface the glory of God (Romans 3:23).  

Love is a cascade, which starts with God and is life-giving (1 John 4:16).  The self-sacrifice of the Lord Jesus Christ was the most loving thing God could do; giving Himself for the people who spurned Him - to bring them back to Him.  The cross not only showed the raw brutality of mankind, but also showed the love of God without any reserve.  That sacrifice was sufficient to atone for the sins of the whole world for all time, as people turn to Him in repentance and faith (1 John 2:2).  That was love.

The only suitable response is to be immensely grateful.  But how do we show that gratitude?  Partly it is in expressing the love He has given to us back to Him in our heart's devotion, like Mary who worshipped Him by welcoming His words (Luke 10:42).  But inner piety is not enough.  After all, the love of the Lord Jesus was a very physical and practical action.   He was determined to do His Father's will (Matthew 26:39-42).  In the same way, our love needs to be first expressed towards His people in practical and tangible ways, in Jesus' Name (Ephesians 5:1-2).

That was what Jesus meant by washing the disciples' feet and telling them to do to others what He had done for them (John 13:14-17).  It was not a new liturgy involving water and feet but a practical example of serving in humility: it was love in action.  Indeed, true love is always 'in action' and sacrificial, or it is not love at all.  How will anybody know what God is like if we do not love them like Jesus did?  A little saying goes like this: ‘The only gospel that others can see is the gospel according to you and to me’!  Genuine, practical, self-giving, other-serving, humble love should be the trademark of the children of God.  Love is made complete when the love God gives to us is shared with others, who return to give glory to Him.  What a challenge!