I likely would not agree with J.I. Packer since I am not Reformed of anything...
He said that "water" and "The Spirit" are two aspects of the same ONE reality: That God's renewal of the fallen and unresponsive human heart is regenerated by the purifying and energizing components -- just as they were set forth in God's promise to renew the Israelite hearts in Ezekiel 36:25-27:
There are no purifying and energizing components in water...
And I'm not claiming anybody finds that there are, other than the obvious, yes, water physically cleanses a person...
May I remind you that "there's no purifying and energizing components in mud/spittle, either" -- yet the Living Word spoken through seemed to do wonders for a man to see.
So now what? Treatises, threads & posts from people militating versus the mud Jesus used to heal a man?
The mud is no different -- a similar common element -- than what we find in Ephesians 5:25-26:
...Christ loved the church and gave himself up for her 26 to make her holy, cleansing her by the washing with water through the word...
If you have a problem with Jesus choosing to use either mud or water, take it up with Him.