Luther comments on today's Psalmody
Psalm 3 is a psalm of prayer in which we follow the example of David. He prayed this prayer in distress when his son Absalom expelled him, and his prayer was granted to him. At the end, David glorifies God for being a true helper and keeper for all of His people who call on Him in distress.
Genesis 42 doesn't record a prayer by Jacob, but he is definitely in distress on account of his sons - first that they got rid of his beloved Joseph, and now that Joseph has demanded Benjamin come to Egypt. In today's New Testament reading (Mark 12:1-12) Jesus speaks of sons of Israel doing more than expelling the Son of David and Son of God from the vineyard. Quite appropriate psalm for today.
Back to father Jacob. He can only see death for his son Benjamin - and his own death by sorrow (Genesis 42:38). But in the end both Benjamin and Joseph will be alive. So also the disciples see only death for Jesus on Good Friday - and their death by sorrow. But after Easter, Jesus is alive - and they have more life than they ever had before. So also us - the Lord calls us to follow His voice, and we see how we have to give up what we think is right, to do things we think will never work, to die to self. But even when we can only see death, in the end this is the path of life with Christ.