To work without attachment is to work without the expectation of reward or fear of any punishment in this world or the next. Work so done is a means to the end, and God is the end.
Different people call on [God] by different names: some as Allah, some as God, and others as Krishna, Siva, and Brahman. It is like the water in a lake. Some drink it at one place and call it 'jal', others at another place and call it 'pani', and still others at a third place and call it 'water'. The Hindus call it 'jal', the Christians 'water', and the Moslems 'pani'. But it is one and the same thing.