People express their feelings for each other in radically different ways. I have seen movies and television shows where a son claims that his father never told him that he loved him, but that it was just always understood. That seems preposterous to me, but I have friends and acquaintances that say that their own family life was very similar to that growing up. Family members simply didn't say, "I love you."
That was and is certainly not the case in my family. I was told that I was loved practically every five minutes. I've carried on that practice with my own wife and children. In families like mine, "I love you" is so frequently used that it really loses some of its force. We use it in place of 'goodbye' when speaking on the phone. We even use it to see if we've offended each other. "I love you?" I might 'ask' sheepishly when trying to see if my wife is upset with me about something.
Now I definitely wouldn't tell someone living in a family like mine, where statements of affection like this are given very freely, that they are doing something wrong, and I'm certainly not going to change this in my own family, but I could imagine some legitimate complaints. "You've turned love into something cheap!" someone might say. Detractors would rightfully point out that it is very easy to tell someone you love them, but actual love is sacrificial. It costs you something. It's hard work.
It can be really complicated to try and figure out how to properly express our love for others - even those closest to us - but what kind of example does God set for us in this pursuit? How does He express His own love toward His creation, toward His people, and toward those that have yet to come to Him in faith and repentance?
What we end up finding is that God uses action far more often than words to express His love. And to be honest, His actions speak a lot louder than words when it comes to proving that He does in fact love His people. He sends His servant Moses to publicly argue with Pharoah for the freedom of the Israelites. And when Pharoah refuses to let them go, God shows up with ten astounding plagues upon the Eyptians to force the issue. Then He parts the sea and escorts them across on dry land, drowning their enemies behind them. After that, He feeds them with bread from heaven while they wander in the wilderness. The Old Testament stories are full of these kinds of displays of God's power on behalf of Israel. He tells His people in Jeremiah 31:36, "If this fixed order [sun, moon, and stars] departs from before me, declares the LORD, then shall the offspring of Israel cease from being a nation before me forever." In other words, if the sun keeps rising every day, then you can rest assured that God still cares.
So if His actions of love have far more impact than a few measly words, then why I am so floored by a verse like Isaiah 43:4? There God says, "Because you are precious in my eyes, and honored, and I love you, I give men in return for you, peoples in exchange for your life." In this passage, God actually uses the very human-sounding 'three little words'! When God uses them here in Isaiah, though, we know that He is not speaking flippantly. At this point in the story, He has already carried His people so mightily and demonstrated His love to them so many times that no one should be able to doubt the sincerity of His words.
Maybe He didn't even need to say this aloud, but I am so glad that He did! I am a student of the Scriptures, so I know of His amazing deeds on behalf of His people - all of which demonstrate His providential love - but I am also a human being, and I need to hear it (or in this case read it) spoken in such simple and earthly terms from time to time. It gives all of His loving acts the proper perspective. We are "precious" in His sight, and He really does love us. We have been taught to trust Him when He speaks, and I am very glad to be able to trust Him when He expresses His tender feelings for His people.
This declaration of God's love doesn't ever come cheaply. It is backed up by incredible acts of compassion, grace, and mercy - including the sacrifice of His Son (the exact imprint of His nature - Hebrews 1:3). And He demonstrates this love over and over again before He ever simply utters the words. That should reinforce the idea all the more in our minds as believers. We are loved!
And we need to carry this message of love to the lost, but when we do, let's do it the way that God does it. Let's give ourselves sacrificially to the cause of helping the poor and needy (James 1:27), and let's teach people about how awesome our God is, and about all that He has done - before we start verbally assuring them over and over again that God loves them. There will be time for that later, when they have seen the evidence of it themselves in the way that we act as His hands and feet.