“My Father is working until now, and I am working”
To this very day My Father is at His work, and I too am working.… Not only was He breaking the Sabbath, but He was even calling God His own Father, making Himself equal with God. (John 5:17–18 BSB)
What it sounds like today
A mild defense that somehow provokes a murder plot.
The cultural key
The theologians of the day had already worked the puzzle: God rested on the seventh day, yet babies are born and rain falls and the wicked die on Sabbaths, so God must keep exercising his providence (giving life, judging) without breaking his own rest; sustaining the world was recognized as God's uniquely permitted Sabbath work. Jesus, challenged for a Sabbath healing, claims exactly that exemption: my Father works on the Sabbath, and I am working the same shift. His hearers do the math instantly, as verse 18 records.
Recovered meaning
Not 'the rules are flexible' but 'I do what only God is allowed to do, because he is my own Father.' The Sabbath dispute was the surface; the equality claim underneath is what they heard, and John confirms they heard it correctly.