There are two aspects of this law – the work and the worker. The work must be worthwhile in itself and be carried to its conclusion; the worker must be honest and energetic and have the right attitude to what he does.
Only if and when the worker can say he has done his very best and the task has been duly completed can he feel satisfied. As Psalm 128:2 puts it, “When you eat the labour of your hands, you shall be happy and it will be well with you”. This reward is subdivided in Pir’kei Avot chapter 4: “You shall be happy in this world and it will be well with you in the world to come”.
If we wanted to take the thought further, we could try to read the mind of the work itself, and say, “When you are handled and performed properly, you will have a smile on your face, and the world will say, ‘This is a happy, satisfied piece of work’”.