Love is commanded in the law and is not an alternative to the law.
The proper understanding of both the goodness and the use of the law must not be forsaken by Christians, many today draw a sharp distinction between the law and love, claiming that we are to follow love not law as a rule of life. But where does God tell us to love, but in the law, for what is the sum of the Ten Commandments but to love the Lord our God with all our heart, with all our soul, with our strength, and with all our mind, and our neighbour as ourselves (Deut 6:5).
Christ upheld this teaching in the New Testament, when asked which is the great commandment in the law answered "Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind. This is the first and great commandment. And the second is like unto it, Thou shalt love thy neighbour as thyself. On these two commandments hang all the law and the prophets." (Matt 22:37-40). The Saviour here shows what God's law requires, and that love summarises the substance of that law.
We can see here in both the Old and New Testaments the duty called for in the law: it is love. What strength of love is called for under the law: it is "with all thy heart". This is not a law that the Christian should ever see as burdensome. Indeed as Ursinus teaches on the Thirty Fourth Lord's Day of his Catechism, "We were also created, and have been redeemed by Christ and regenerated by the Holy Spirit, that we might keep this law, or love God and our neighbour as it requires, both in this and the life to come"."I write no new commandment unto you, but an old commandment which ye had from the beginning." (John 2:7)
As the Puritan Thomas Watson notes 'love is the soul of religion, and that which constitutes a real Christian'.