Who is the thief who comes to steal and destroy? Not the devil.

Craig Keener on John 10:10

Many people assume that the thief in John 10:10 is the devil, but they assume this because they have heard this view many times, not because they examined the text carefully in context. Of course, the devil does come to steal, to kill, and to destroy; but we often quote the verse this way and miss the text’s direct applications because we have not stopped to read the verse in context.

When Jesus speaks of “the thief,” he speaks from a larger context of thieves, robbers, wolves, and strangers who come to harm the sheep (10:1, 5, 8, 10, 12). In this context, those who came before Jesus, claiming his authority, were thieves and robbers (10:8); these tried to approach the sheep without going through the shepherd (10:1). This was because they wanted to exploit the sheep, whereas Jesus was prepared to die defending his sheep from these thieves, robbers, and wolves.

I must admit that I too thought the "thief" was the devil and I appreciate Craig showing the context for a better understanding. You can read the rest here.