Romans 11:29-36 / Luke 14:12-14
We don't like to feel indebted to someone or beholden to someone.
We don't have this feeling of freedom whether be it simply just owing thanks or having a duty to someone in return for help or a service.
Also because we want to do everything on our own resources and not dependent on anyone.
In the 1st reading, it seems that God wants to make us indebted to Him or beholden to Him when it says in this line: God has imprisoned all men in their own disobedience only to show mercy to all mankind.
But the truth is that we disobey God and fall into sin because we want to be independent and free to do what we want.
But the fact is that we cannot be totally independent from our Creator, nor can we have that total freedom to do whatever we want.
And the point is that when we fall into sin, there is also no way to get out of it with just our will-power or on our own strength.
We need the mercy of God. We do not deserve it and have no right to it. Yet God gives it freely when we ask for it.
In that sense we are indebted and beholden to God. We need His mercy if we want to be saved. We can't save ourselves.
And because we can't save ourselves, neither can we save others or make them indebted or beholden to us.
That is what Jesus is saying in the gospel. What we have freely received, we also must freely give.
When we understand that is how it is with God's mercy, we too will be merciful. We will understand the saving love of God and also lead others to understand His saving love.