He will answer them, ‘Amen, I say to you, what you did not do for one of these least ones, you did not do for me.’ (Mt 25:31-46)
https://bible.usccb.org/bible/readings/030722.cfm
In the general confession of sins at the beginning of the Mass, we acknowledge that we have greatly sinned not only in what we have done, but also in what we have failed to do. Sometimes what we fail to do is often more important than the things we have done. And so we pray for Ukraine.