General Information:

Joseph tells his brothers about his dream.

Behold

The word "behold" here alerts us to pay attention to the surprising information that follows.

The word "we" refers to Joseph and includes all of his brothers. (See: rc://en/ta/man/translate/figs-exclusive)

When grain is reaped it is tied into bundles and stacked until it is time to separate the grain from the straw.

Here the word "behold" here shows that Joseph was surprised by what he saw.

Here the bundles of grain are standing and kneeling as if they were people. These bundle represent Joseph and his brothers. (See: rc://en/ta/man/translate/figs-personification)