Romans 12:4 For as we have many members in one body, and all members have not the same office:
https://gbcnewberg.org/sermons/one-body-many-parts/
Everyone as a complete human has all parts that helps in accomplishing one task or the other at a time and according to how it's created and the purpose for which it is created. 
That's why the hand is there just to do the work meant for the hand and dare not try to do the one meant for nose, have you ever imagine testing a food with your eye hmmmm we all know how it will feel like and that's why it allow the tongue do it's job so also will the heart not try to do the work of the intestine so it does it part and allow the intestine to do it's part, ear can never take in something either as food or even liquid so the mouth is responsible for that without the fear of contradictions every part carries out it's duty perfectly as the eyes or any other part can't tell the hand that it doesn't know how to do it's work as there is no part that can do the work of the hand and like wise the hand too can't tell part how to carry out its duty.
All these are but few that one will mention in the body of a man.
Now God has used this as a perfect decribsion of how the work in His vain yard should look like. As every worker has a roll to play in that yard and without any fear of contradictions every roll is perfectly merged with the person that is created for that purpose. That's why he mentioned in Romans 12:6 Having then gifts differing according to the grace that is given to us, whether prophecy, let us prophesy according to the proportion of faith;
Romans 12:7 Or ministry, let us wait on our ministering: or he that teacheth, on teaching;
Romans 12:8 Or he that exhorteth, on exhortation: he that giveth, let him do it with simplicity; he that ruleth, with diligence; he that sheweth mercy, with cheerfulness.
All this are work been given by christ and it's of course according to the level of our faith we must all do this to propagate the gospel to ends of the world.
Doing this must be in harmony and togetherness so as to achieve that goal that is set before us by Christ him self as the body is made of different part but they do it for them selves making the whole body to grow so also is God expecting us to carry out our duty to make the body of Christ grow.keeping it with this scripture.Romans 12:10 Be kindly affectioned one to another with brotherly love; in honour preferring one another;. By so doing we will rejoice one day as we will be called Faithful servant. May our labour never be in vain on earth. Amen