When anyone asks the above question it's usually because someone has tried
to get them to believe that they have to keep the ten commandments to be saved
and used that statement as an argument!
Let's analyse this.
The first four commandments state that ...
But, when we think of the natural human mind it can be shown that we can keep any or all of these commandments, to our human satisfaction, without love being our motive!
At the start we see that love is not mentioned as a requirement or suggested as a possibility within the ten laws! Looking at the laws one notices for instance that, 'having no other Gods but Jehovah', because He is a jealous God, can readily be agreed to out of fear and with a heart full of resentment. The same applies to the other three also. Love is not a requirement for keeping these laws! So how can one say that love summarises them!
Similarly let's look at the last six commandments...Exo 20:12 Honor your father and your mother, so that your days may be long on the land.
Exo 20:13 You shall not murder.
Exo 20:14 You shall not commit adultery.
Exo 20:15 You shall not steal.
Exo 20:16 You shall not testify a falsehood against your neighbor.
Exo 20:17 You shall not covet anything which belongs to your neighbor.
One can find a simple reason to follow all of these besides love; self interest and fear of loss for instance! A simple desire to hang on to whatever may be on offer and not lose out through being caught doing wrong!
Love is not a requirement for attempted commandment keeping, so love
is not a summary of the law!
Of course, one can think that one is acting out of 'love' when one is attempting to keep them. Why else would one not commit adultery or covet some other thing? Surely 'not having opportunity' or 'being scared of the consequences', would not be part of one's thinking!
In fact the scriptures say that "All have sinned and fallen short of the glory of God! The ten commandments were given to show you that you cannot 'do' right. In fact that attempted right-doing is self-righteousness and does not bring God's righteousness.
We can see what is said about this in the Bible in Phillipians 3:8-9...
Phillipians 3:8-9 More than that I also consider all things to be loss for the excellence of the knowledge of Christ Jesus my Lord, for whom I have sustained the loss of all things, and I consider them to be rubbish, in order that I may gain Christ and be found in Him, not having my own (self) righteousness, the righteousness of the law, but the righteousness by faith in Christ, the righteousness which is from God by faith;
Notice that any righteousness you have through living by the law is your own righteousness; and this is what Isaiah says about our righteousness...
Isa 64:6 But we are all as an unclean thing, and all our righteousnesses are as filthy rags;
The only righteousness that God will accept is that which comes as a gift from Jesus through grace, so it's having Jesus live in us that will cause all our actions and thoughts to be based on righteousness and love.
The error in thinking, I believe, comes about because some can wrongly imagine, for instance, that love of neighbour and the last six commands form an equation. That isn't what the bible says. Love of neighbour includes these things but takes in much more also because it's Jesus in us providing the motivation and the grace. Since it's not an equation one cannot reverse the order of the statements and imagine that it balances. The last six commands do not equal love of one's neighbour; they are much, much less than the love that is required! That is why 'Love' is the Christian standard for behavior and not Law.
The love that we are to exhibit as Christians is the self-sacrificing love that Jesus showed in His life - being willing to die for His enemies.
The love of God is shown fully when Jesus lives 'in' and 'through' us. In other words when we live by 'grace' through 'faith' in our Lord. We, as Christians, are to love one another as Jesus loved us (ie. with Jesus' love), not just with the love we can work up for ourselves (love with all your heart), and even lower down would be to love at the ten commandments level of (ie. try not to kill anyone!).
John 13:34-35 “A new command I give you: Love one another. As I have loved you, so you must love one another. By this everyone will know that you are my disciples, if you love one another.”
When we live with and in the love of God, by the Holy Spirit, then everything is done out of love.
Best wishes for Grace and the Peace of Jesus.