All passages referenced here will be from the New King James Version of the Bible. I hope in the name of our eternal Lord and Savior Jesus Christ that this will bless you.
The Holy Bible is very unambiguous and direct when combining passages such as this one with the moral of the entire Scripture. Both before and after this verse it mentions being strengthened through His Spirit in the "inner man," and "to know the love of Christ which passes knowledge." The inner man is the part of us which delights in the law of God. What Christ did for us required a love that no one else possessed. He lived a sin-free life, knowing the end from the beginning, that He would take our place on the Cross that we might have life. This type of love only comes from God. In 1 Corinthians 13:1-10 it explains how love is the substance of all gifts and abilities that one may enjoy from God as a follower of Christ, and that without love we have missed the purpose of these gifts.
To directly answer your question:
Paul is challenging the Ephesians and all who read this Epistle to be grounded in love:
For all the law is fulfilled in one word, even in this: 'You shall love your neighbor as yourself.'
-- Galatians 5:14
The Holy Spirit whom Jesus gave unto His Holy Apostles and all those who serve Him and ask of the Father for the Holy Spirit spoke this word through Paul to the entire Church. Thus, since the Holy Spirit is the one speaking, we may call into remembrance what Jesus said:
But the Helper, the Holy Spirit, whom the Father will send in My name, He will teach you all things, and bring to your remembrance all things that I said to you.
-- John 14:26
If we look at Luke 10:27-28 we see that loving God and His people leads to life. Who else can fulfill this other than those who love God's risen Son Jesus Christ, who truly is God in the flesh, and have the love of Christ within them.
Just as Christ says:
If you keep My commandments, you will abide in My love, just as I have kept My Father's commandments and abide in His love. These things I have spoken to you, that My joy may remain in you, and that your joy may be full. This is My commandment, that you love one another as I have loved you.
-- John 15:10-12
We are called to love one another just as Christ loved us, who used every ounce of His gifts and strength to give us eternal life through the shedding of His own innocent blood. This type of love is the love of Christ, and is very rare in this world.
We as Christians only have the power to save souls from death, just as we were saved, when we love all others just as Christ loved us. When we are born again, of the Spirit, we are to put away our old lives and identities and take on the full armor of God by living just as Jesus Christ lives. This is the perfection of a Christian. To become Christ-like in all word and deed, and is achieved by a complete unrelenting love of God and His people.
In Jesus Christ's name. Amen.