How to avoid storing rsa passphrase

I'm writing a program that is executed by cron throughout the day.

It has to use a RSA identity file to connect to another server (using jcraft's jsch). If I perform the procedure by hand on the command line, it involves entering a passphrase to decrypt the private key.

What is a secure solution that does not involve coding the passphrase somewhere in the code?

An idea I have is just to store the identity file unencrypted, and make sure that the file has its permission set securely.