Six at the bottom of the cauldron is the image of its legs. Corresponding above with the fourth line, with legs pointing upward, is the image of being overturned.
When a cauldron is overturned, its legs are inverted; when its legs are inverted, its contents spill out, which is not the normal course.
Yet there is a time when overturning is proper—namely, pouring out spoiled and foul dregs to achieve cleanliness and take in the new, which is acceptable. Therefore, in overturning the legs, the benefit lies in removing the foul. Foul means bad or spoiled.
The fourth line is close to the ruler, in the position of a high minister; the initial line is a person below, and their correspondence means that the superior seeks from the subordinate and the subordinate follows their superior.
If the superior can employ the excellence of the subordinate, and the subordinate can assist the actions of the superior, they can achieve great merit, which is a good path—just as the cauldron's overturning legs has a time when overturning is proper and is not contrary to reason.
'Taking a concubine for the sake of her son, no blame': Six is yin and lowly, hence it is a concubine. 'Taking a concubine' means obtaining the right person; if one obtains a good concubine, she can assist her master so that he incurs no fault or blame.
'Son' means the master; through her son, she brings her master to no blame. Six is a yin line dwelling below, humble and gently yielding to yang, which is the image of a concubine.
Because Six corresponds above with Nine in the Fourth Place, representing overturning legs, this meaning is developed.
Six at the Beginning originally has no talent or virtue worthy of praise, hence it says 'taking a concubine,' meaning if one obtains the right person, it will be like this.