Man's mercy pales in comparison to God's mercy.
"After this, Jesus, knowing that all was now finished, said (to fulfill the Scripture), 'I thirst.' A jar full of sour wine stood there, so they put a sponge full of the sour wine on a hyssop branch and held it to his mouth. When Jesus had received the sour wine, he said, 'It is finished,' and he bowed his head and gave up his spirit." - John 19:28-30 ESV
I always thought this was curious. Jesus holds this glorious knowledge in His conscious mind at a time where He is physically at His weakest and purposely brings Himself, at great pains, to say, 'I Thirst'. He wasn't asking for help. He was making a statement and the scripture gives us a reason why He said what He did. It was to fulfill scripture. Here are the scriptures that refer to the Messiah's thirst and the use of vinegar.
"I am poured out like water, and all my bones are out of joint; my heart is like wax; it is melted within my breast; my strength is dried up like a potsherd, and my tongue sticks to my jaws; you lay me in the dust of death." - Psalms 22:14-15 ESV
"Reproaches have broken my heart, so that I am in despair. I looked for pity, but there was none, and for comforters, but I found none. They gave me poison for food, and for my thirst they gave me sour wine to drink." - Psalms 69:20-21 ESV
Man's mercy is the nobility of the powerless. Man wants to ease pain. Sour wine is a trick. It dulls the thirst while doing nothing for the dehydration.
God for His own reasons still wanted to showcase man's response even with the full knowledge of the completion of the payment for sin in mind. John's gospel is an eagle eye's view of redemption.
Here is what the man sees (Matthew's account).
"And one of them at once ran and took a sponge, filled it with sour wine, and put it on a reed and gave it to him to drink. But the others said, 'Wait, let us see whether Elijah will come to save him.'
And Jesus cried out again with a loud voice and yielded up his spirit. And behold, the curtain of the temple was torn in two, from top to bottom. And the earth shook, and the rocks were split. The tombs also were opened. And many bodies of the saints who had fallen asleep were raised, and coming out of the tombs after his resurrection they went into the holy city and appeared to many." - Matthew 27:48-53 ESV
God's mercy opens access, shakes the Earth, splits rocks and opens tombs bringing people back to life. That is God's response to 'I thirst.'
Let's hold the knowledge of the Finished Work of Christ in our mind and bring our thirst to God. Thirst for love... thirst for trust... thirst for help... thirst for change... God has an answer and He will split the rocks to make sure it gets to us. He will shake the Earth and open the graves to bring life out of places that once held only death.