Matthew 18

To those that hold the priesthood and in many cases, in priesthood leadership, the Savior teaches some important doctrine .  First, after the Savior rebuked the devil in the lunatik child, His disciples asked -

"...Why could not we cast him out?"  (New Testament | Matthew 17:19)

Having been given authority to do so, the Savior teaches these priesthood holder additional requirements, answering -

"Because of your unbelief: for verily I say unto you, If ye have faith as a grain of mustard seed, ye shall say unto this mountain, Remove hence to yonder place; and it shall remove; and nothing shall be impossible unto you.
21 Howbeit this kind goeth not out but by prayer and fasting."  (New Testament | Matthew 17:20 - 21)

The exercise of priesthood requires then faith, and in many cases, fasting and prayer.

Second, the disciples asked the Savior -

"...Who is the greatest in the kingdom of heaven?"  (New Testament | Matthew 18:1)

Which seems a natural thought in this world of a desire for power and authority.  To which the Savior responded as He -

"...called a little child unto him, and set him in the midst of them,
3 And said, Verily I say unto you, Except ye be converted, and become as little children, ye shall not enter into the kingdom of heaven.
4 Whosoever therefore shall humble himself as this little child, the same is greatest in the kingdom of heaven."  (New Testament | Matthew 18:2 - 4)

In my mind, the Savior is teaching that we must become as a little child is submissive and obedient.  It doesn't matter where we served but how we serve.