John 5:18 says:
This made the Jews still more determined to kill him, because he was not only breaking the Sabbath, but, by calling God his own Father, he claimed equality with God.
The typical interpretation is that Jesus has just made an extraordinary claim about his own identity. By calling God his Father, Jesus is claiming to possess the same divine status or nature as God. The Jewish leaders understand the implication: Jesus is claiming equality with God. Their attempt to kill him is therefore not merely about Sabbath breaking, but about what they perceive as blasphemy. On this reading, “equality with God” is essentially a statement about who Jesus is.
But that interpretation asks the word “equal” to carry considerably more meaning than the Greek itself contains.
Equal, ἴσος (isos) in Greek, means equal, equivalent, or the same in some relevant respect. It does not inherently mean identical in nature, essence, or being. The dimension of equality has to come from context.
The same construction appears in Matthew 20:12, where workers complain that the landowner “made them equal to us” after paying everyone the same wage. The workers obviously do not mean that the other workers have become equal to them in every conceivable respect. They have been made equal in the matter being disputed: their compensation.
The matter being disputed in John 5 is equally obvious: working on the Sabbath.
Jesus has just healed a man on the Sabbath. The religious authorities object. Jesus responds:
“My Father is working until now, and I am working.”
The logic may be much simpler than the traditional interpretation makes it.
The Sabbath is a rule governing human beings. Genesis says that God rested after creation, but nowhere suggests that God subsequently stops working every seventh day. God continues sustaining the world, giving life and doing good regardless of what day it is.
Jesus makes essentially the same point elsewhere:
“The Sabbath was made for man, not man for the Sabbath.”
Notice what he does not say. He does not say that humanity was created to obey the Sabbath. He says the opposite. The Sabbath came into existence for the sake of human beings. The institution serves people; people do not serve the institution.
So when religious authorities condemn Jesus for doing good because it happens to be the Sabbath, his response can be read as remarkably straightforward:
God keeps working. So will I.
Their doctrine has taken a rule intended for human benefit and elevated it above the obvious reality it was supposed to serve.
That makes John’s description of their reaction particularly interesting:
ἴσον ἑαυτὸν ποιῶν τῷ θεῷ
Literally:
“making himself equal to God.”
But equal in what respect?
The preceding sentence has just supplied one:
“My Father is working until now, and I am working.”
God works. Jesus works.
Jesus has put himself on equal footing with God concerning the exact rule under dispute. The religious authorities insist that Jesus must stop working because it is the Sabbath. Jesus points to the obvious counterexample: God himself does not stop working on the Sabbath. And Jesus refuses to stop doing good merely because their religious doctrine says that he should.
This also explains naturally why the confrontation becomes so threatening. Jesus is not merely violating one Sabbath rule. He is challenging the entire legalistic reasoning behind it. The authorities claim that their interpretation represents God’s will. Jesus points out that their interpretation does not even describe God’s own behavior.
Nothing in ἴσος itself requires John to be saying that Jesus was claiming equality of divine essence. That is a theological interpretation of the sentence, not the meaning contained in the Greek word. In context, the equality can be much more immediate: equality regarding Sabbath work.
A retranslation that preserves that contextual connection could therefore be:
This made the Jews still more determined to kill him, because not only was he breaking the Sabbath, but he justified it by pointing out that God himself worked on the Sabbath too, giving himself a freedom they believed should belong to God alone.