Whereas some people refuse to believe something about God or some Christian doctrine except if they can find it straightforwardly affirmed in some propositional manner, it seems the Jews learned about God in large part by interpreting his actions. So for example, consider what Ps 103 says about God:
The LORD works vindication and justice for all who are opposed.
He made known his ways to Moses,
his acts to the people of Israel.
The LORD is merciful and gracious,
slow to anger and abounding in steadfast love.
He will not always accuse,
nor will he keep his anger forever.
He does not deal with us according to our sins,
nor repay us according to our iniquities.
For as the heavens are high above the earth,
so great is his steadfast love toward those who fear him;
as far as the east is from the west,
so far he removes our transgressions from us.
As a father has compassion for his children,
so the LORD has compassion for those who fear him.
For he knows how we were made;
he remembers that we are dust (Ps 103.6-14).
Look at the theologizing this psalmist does, merely out of the fact of the Exodus! He has no problem affirming God's fundamental commitment to justice for all oppressed persons, the limits on his anger and accusation compared to the limitlessness of his love and mercy, his moral fairness and awareness of human weaknesses and shortcomings, and so on. The psalmist had no single text to which to appeal which explicitly spells all these things out. He sees these things about God in the act of the Exodus itself.
There is nothing wrong with this. We learn about people by what they tell us, but also by what they do. Things are no different for God. And the things the psalmist learn are quite powerful: God's mercy far outweighs his anger, and his goodness is permanent beyond his accusations.
Now someone may suggested that these conclusions only apply to the righteous who keep God's law, not to all persons in general. So David writes at vv. 17-8: But the steadfast love of the LORD is from everlasting to everlasting on those who fear him, and his righteousness to children's children, to those who keep his covenant and remember to do his commandments. But there are plenty of good reasons to think that actually God's love and mercy are even greater than David here imagines.
First, of course, there is the fact that the same sentiments are echoed by Jeremiah in the Lamentations precisely in the context of the punishment of unfaithful, wicked covenant-breakers. After the covenant curse had come upon God's people for their faithlessness, Jeremiah has the gall to insist:
I am one who has seen affliction
under the rod of God's wrath. . .
But this I call to mind,
and therefore I have hope.
The steadfast love of the LORD never ceases,
his mercies never come to an end;
they are new every morning;
great is your faithfulness.
"The LORD is my portion," says my soul,
"therefore I will hope in him."
The LORD is good to those who who wait for him,
to the soul that seeks him.
It is good that one should wait quietly
for the salvation of the LORD.
It is good for one to bear
the yoke in youth,
to sit alone in silence
when the LORD has imposed it,
to put one's mouth to the dust
(there may yet be hope),
to give one's cheek to the smiter,
and be filled with insults.
For the LORD will not
Although he causes grief, he will have compassion,
according to the abundance of his steadfast love;
for he does not willingly afflict
or grieve anyone (Lam 3.1, 21-33).
Here we see appeal to the superiority of God's goodness over wrath precisely in the context in which the covenant curse is being suffered. God's goodness is greater than his wrath even in the case of the wicked who break his covenant and do not remember his commandments.
Moreover, we find in the New Testament the revelation that God loves us even while we were still sinners (Rom 5.8), even to the point of dying for our sins in our place! If anything can be a proof of the superiority of God's goodness over his wrath, this would be it! And it would not be fundamentally mistaken or out of place to read this into God's actions on the cross. For if David can get so much out of the Exodus, in which God does the killing rather than the dying, how much more can we understood about God's goodness from his death in Jesus Christ on our behalf!