The mountain is the oldest image of the hierarchy of value, and service is only accepted at its height. A scattered people is gathered to the one high place, because worship that means anything has to aim at the top of things rather than at whatever is nearest. What is offered there is the firstfruits, the first and best of the increase, handed over before a man keeps any for himself. The leftovers do not reach the summit.
To give the firstfruits is to put the highest good ahead of your own appetite in the very order of your acts. That priority is what gets a life accepted. A person climbs toward what is highest and lays the best of himself down at the peak of it. Bring your first and finest to the top of the mountain, and you are received there.