Do not love in word only or tongue only

When the venerable John could no longer walk to the meetings of the Church but was borne thither by his disciples, he always uttered the same address to the Church; he reminded them of that one commandment which he had received from Christ Himself, as comprising all the rest, and forming the distinction of the new covenant, “My little children, love one another.” When the brethren present, wearied of hearing the same thing so often, asked why he always repeated the same thing, he replied, “Because it is the commandment of the Lord, and if this one thing be attained, it is enough” [Jerome]. Jamieson-Fausset-Brown Bible Commentary

This is how we know what love is: Jesus Christ laid down his life for us. And we ought to lay down our lives for our brothers and sisters. If anyone has material possessions and sees a brother or sister in need but has no pity on them, how can the love of God be in that person? Dear children, let us not love with words3056 or speech1100 but with actions and in truth. (1 John 3:16-18)

3056. logos
a word (as embodying an idea), a statement, a speech
1100. glóssa
the tongue, a language, a nation (usually distinguished by their speech)

One may love in word only, and yet the affectionate words may be quite sincere; and this is a common case. People say kind things which they mean at the moment, but afterwards they do not take the trouble to act kindly. But to love with the tongue only is far worse. This is to say kind things which one does not mean, and which one knows to be unreal. Deeds are needed to complete the kind word; truth is needed to correct the insincere tongue. Pulpit Commentary

Gill’s Exposition of the Entire Bible

This is how we know that we belong to the truth and how we set our hearts at rest in his presence: If our hearts condemn us, we know that God is greater than our hearts, and he knows everything. Dear friends, if our hearts do not condemn us, we have confidence before God and receive from him anything we ask, because we keep his commands and do what pleases him. And this is his command: to believe in the name of his Son, Jesus Christ, and to love one another as he commanded us. The one who keeps God’s commands lives in him, and he in them. And this is how we know that he lives in us: We know it by the Spirit he gave us. (1 John 3:19-24)

3:16-21 Here is the condescension, the miracle, the mystery of Divine love, that God would redeem the church with his own blood. Surely we should love those whom God has loved, and so loved. The Holy Spirit, grieved at selfishness, will leave the selfish heart without comfort, and full of darkness and terror. By what can it be known that a man has a true sense of the love of Christ for perishing sinners, or that the love of God has been planted in his heart by the Holy Spirit, if the love of the world and its good overcomes the feelings of compassion to a perishing brother? Every instance of this selfishness must weaken the evidences of a man’s conversion; when habitual and allowed, it must decide against him. If conscience condemn us in known sin, or the neglect of known duty, God does so too. Let conscience therefore be well-informed, be heard, and diligently attended to. Matthew Henry’s Concise Commentary