Posted by Richard on UTC 2016-05-01 07:49.
Weber's starting point for his analysis is the idea of work as a 'calling', as a Beruf, for it was Luther himself who gave currency to the word Beruf in his great translation of the Bible, a translation that became the basis of standard modern German.
Literally, Beruf and its equivalent Berufung means 'something to which one is called or summoned'. Nowadays in German Beruf has lost its Lutheran etymological radiance and is translated without a further thought as 'occupation' or, even more inaccurately, simply as 'job'. Was sind Sie von Beruf? is now just the harmless way of asking 'what's your occupation?', 'what do you do?'. Even in English the now rare expression 'calling' would probably no longer have an immediately religious meaning to the hearer, being understood to be a personal obsession of the individual and not a summons from God.
For Luther, however, your role in life was God-given, so that for him Was sind Sie vom Beruf? would mean more or less 'To what have you been called?'.
Weber notes that, as Protestantism developed, in whatever flavour – Lutherans, Calvinists, Pietists, Puritans, Methodists and Baptists – work and economic activity according to one's abilities became the central 'calling' of human life.
The only way of living acceptably to God was not simply outdoing worldly morality by monastic asceticism, but rather consisted entirely in the individual's fulfilment of the obligations imposed upon him by his position in the world, that is, in effect, his 'calling'. 
Such a calling is not the same as greed motivated solely by the desire for wealth – there was plenty of greed around in the Austrian Empire. On the contrary, a worker (whether owner or employee) who believed in the redemptive value of work in itself and who did not just view it as an instrument for survival or gain was much more adaptive and efficient.
Work for yourself or for others?
Luther, a monk, praised work, but his praise for work is not capitalist as we would understand it. We can hardly expect this from him, since he initially belonged to the Order of Saint Augustine, an order that was about as non-capitalist as one could be: solitude instead of social life, penance instead of activity, poverty instead of wealth creation and begging instead of work. However, he swept his earlier monasticism away:
The monastic lifestyle is obviously not just completely worthless as a justification before God but is also, as far as He is concerned, a product of an egoistic lack of love that arises from the renunciation of worldly duties. In contrast to that, the worldly work of the calling appears as an external expression of brotherly love, an unworldy position in almost grotesque opposition to Adam Smith's famous statement [*], but justified by the division of labour that forces every individual to work for someone else. 
Although Luther has not arrived at a capitalist understanding of work and profit, his ideas were revolutionary.
It is almost a platitude that this moral view of the wordly life of work was one of the most consequential effects of the Reformation and that Luther's part in its creation was especially beyond doubt. 
Weber contrasts Luther's theology of daily life with the otherworldliness of Blaise Pascal (1623-1662) who, after his mathematical and scientific breakthroughs, turned to Catholic theology:
[Luther's viewpoint] is worlds away from the deep hatred that Pascal, with his contemplative disposition, had for worldly activities. For him, such worldly things could only be explained by the operation of vanity or cunning. 
Nevertheless, Luther never freed himself from a number of deeply anti-capitalist ideas: the opposition to usury – indeed interest-taking in general; the opposition to wealth beyond immediate personal need – 'Give us this day our daily bread'; the idea that one's station in life was God-given, to be accepted and not changed. We shall also leave his vicious antisemitism unexplored here.
But he was a brave man who held aloft a torch in dangerous times, a torch which would now be carried much further by others.