“Therefore whatever you want others to do for you, do so for them” Matt. 7:12.
The universal language is the language of action.
You can know another has a kind heart by the encouraging letter or deed because you can see the kindness. We can understand how much you love your family because your love for them takes form in the hard working faithful devotion to meeting their needs and protecting them from harm.
God revealed His love in this same way. For century upon century God spoke His wisdom to men through words given to prophets, priests, and saints. The difficulty was that men were not sure what God was really like until He spoke to them in a new way: “And the word became flesh, and dwelt among us, and we beheld His glory, full of grace and truth.”(John 1:14)
God’s love took form in a life of love we could see.
If you want to tell someone that you love them, say as little as possible about it, and show them in loving action.