# Take these men and purify yourself with them

They had to make themselves ritually pure so they could worship in the temple. 

# pay their expenses for them

"pay for what they will need." The expenses would go toward buying a male and female lamb, a ram, and grain and drink offerings.

# they may shave their heads

This was a sign that the person had completed what they promised God they would do. 

# the things they have been told about you

"the things that people are saying about you"