According to the Old Testament, mercy has certain meanings: to stoop in kindness to an inferior, to have pity upon and to be actively compassionate. It used to be a verb form of the word compassion, but we don’t use it anymore—maybe because we don’t have the concept anymore. God actively “compassionates” suffering men—I like that wonderfully well. For God to feel compassion at a distance is one thing, but for God to be actively compassionate with people is something else. Read what the Word of God says about it:

And the children of Israel sighed by reason of the bondage, and they cried, and their cry came up unto God by reason of the bondage. And God heard their groaning, and God remembered his covenant with Abraham, with Isaac, and with Jacob. And God looked upon the children of Israel, and God had respect unto them. (Exodus 2:23–25)

That is at the close of the second chapter of Exodus. And the third chapter opens with the burning bush and goes on to the commissioning of Moses to go deliver Israel from Egypt.
When God actively exercised compassion on these people He did four things: He heard their groanings; He remembered His covenant; He looked upon their sufferings and pitied them; and He immediately came down to help them. The same thing is true in the New Testament, where it is said of our Lord Jesus that when He saw the multitude, He “was moved with compassion toward them, because they were as sheep not having a shepherd” (Mark 6:34). He said to the disciples, “Give ye them to eat” (6:37). That is being actively compassionate.

A great many people are very merciful in their beds, in their lovely living rooms, in their new cars. They have compassion (a noun), but they never “compassionate” (a verb). They read something in the newspaper about somebody suffering and say, “Aw, isn’t that terrible! That poor family was burned out and they’re out on the street with no place to go,” and then they turn the radio on and listen to some program. They’re very compassionate—for a minute and a half—but they don’t “compassionate”; that is, they don’t do anything about it. But God’s compassion leads Him to actively “compassionate.” He did it by sending Moses down to deliver the children of Israel.
One fact about the mercy of God is that it never began to be. I’ve heard of men who were hardhearted or careless, but they began to get stirred up and mercy blossomed forth. It never was so of God. God never lay in lethargy without His compassion. God’s mercy is simply what God is—uncreated and eternal. It never began to be; it always was. Heaven and earth were yet unmade and the stars were yet unformed and all that space men are talking about now was only a thought in the mind of God. God was as merciful as He is now. And not only did it never begin to be, but the mercy of God also has never been any more than it is now.

A. W. Tozer and David E. Fessenden, The Attributes of God: A Jouney into the Father’s Heart, vol. 1 (Camp Hill, PA: WingSpread, 2003–), 79–81.