2. A notable defection 78:9-11

It is difficult to identify the occasion that these verses describe certainly. Ephraim was not only the name of one tribe in Israel. It was also the name of the northern nation of Israel after the kingdom split in Rehoboam's day. Assuming the writer was a contemporary of David the tribe appears to be in view here. In any case the writer used this incident as a bad example that his hearers should avoid.