Su 素: in early texts almost exclusively used as a descriptive adjective: ‘unadorned, plain, not processed or modified’. This also means that what follows it is a noun, an object. We already see this usage on bronze inscriptions from around 600BC, where it appears in lists of gifts from the king to the owner of the bronze vessel, who had it cast to commemorate the event (see for instance the Shi Ke xu 師克盨; Yang Xiaoneng, ‘The Shi Ke Xu: Reconsideration of an Inscribed Late Western Zhou Ritual Vessel’, Artibus Asiae, Vol. 52, No. 3/4 (1992), pp. 163-214. See also this article). In the same way it is used in the Liji 禮記:
A Great or other officer, leaving his state, should not take his vessels of sacrifice with him across the boundary. The former will leave his vessels for the time with another Great officer, and the latter his with another officer. A Great or other officer, leaving his state, on crossing the boundary, should prepare a place for an altar, and wail there, looking in the direction of the state. He should wear his white upper garment and white lower, and his white cap, remove his (ornamental) collar, wear shoes of untanned leather, have a covering of white (dog’s-fur) for his cross-board, and leave his horses manes undressed. He should not trim his nails or beard, nor make an offering at his (spare) meals. He should not say to any one that he is not chargeable with guilt, nor have any of his women approach him. After three months he will return to his usual dress.
(tr. James Legge, modified)
Personally I would not have chosen ‘white’ as a translation of su 素. I think it refers to plain, uncoloured, raw material.
What is more interesting is that the combination 素履 from line 1 is also seen in the Lüshi Chunqiu 呂氏春秋, ‘Master Lü’s Spring and Autumn Annals’:
In the time of Duke Zhuang of Qi there was a knight called Bin Beiju, the “Outsider Who Affronts Everyone.” One night he dreamt of a robust youth who wore a cap of undyed silk with strings of red hemp, a cloak of coarse sackcloth, new shoes of plain silk, and a black-scabbarded sword…
– John Knoblock & Jeffrey Riegel, The Annals of Lü Buwei, p. 478
Knoblock and Riegel read it as shoes made from silk but that doesn’t really fit the material that precedes it – hemp, sackcloth. In this context I expect the shoes to be made of much simpler material than silk. Either way, 素履 in line 1 might also refer to shoes made of plain material.
In the Judgement text lü 履 is a verb, but in the context of line 1 this is not possible, especially because 素履 is followed by the verb wang 往, ‘to go in a certain direction’.
Wujiu 无咎: see third line of hexagram 1.
Going (wearing) plain shoes.
No curse from the ancestors.