Hexagram 08, line 5

顯比。王用三驅。失前禽。邑人不誡。吉。

Xian 顯: appear, become visible, make public, (to) display,  (to) manifest. Also a loan for xin 欣, ‘joyful (appearance)’. Xianbi 顯比 can mean that the alliance is made public.

Sanqu 三驅: a ceremonial royal hunt with specific features. It is mentioned in the Wen Xuan 文選:

若乃順時節而蒐狩, (…)
然後舉烽伐鼓,
申令三驅. (…)
樂不極盤,
殺不盡物.
In accord with the seasons they perform the ritual hunts, (…)
Then, raising the beacons, beating the drums，
They order the three-sided battu to begin. (…)
They enjoy themselves, but not to extremes;
They kill, but do not destroy everything in sight.
– Tr. David Knechtges, Wen Xuan or Selections of Refined Literature, Vol. 1, p. 157-163

Knechtges says about the sanqu:

There are basically two explanations of sanqu 三驅. One, mentioned in the Classic of Changes (Hexagram 8, 9/5), and repeated by Zheng Xuan 鄭玄 (a.d. 127-200)，Wang Bi 王弼 （a.d. 226—249), and Kong Yingda 孔穎達 (a.d. 574-648), is that qu means a three-sided battu in which the beaters drive the game from three sides and leave one side open to allow some animals to escape. It was thought that this practice was an indication of the ruler’s humane desire not to exterminate everything. (…) The second explanation equates san qu with the san tian 三田 (“three hunts”), each conducted in a different season (according to this scheme there was no summer hunt) for a specific purpose: 1) to provide cured meat for the sacrificial vessels; 2) to entertain guests; 3) to fill the ruler’s larder. (…) Since the meaning of qu is “to drive” or “to chase”, the proper meaning of san qu clearly must be three-sided battu.”
(p. 160)

The second explanation is followed by Lu Deming 陸德明 (556-627) in his 周易音義 where he quotes Ma Rong 馬融 (78-186): 三驅者，一曰乾豆 ，二曰賓客，三曰君庖. I can not reconcile this meaning with the next phrase 失前禽 that follows 王用三驅.

Elsewhere in the Wen Xuan the sanqu is mentioned again, in relation to a kind emperor who does not kill excessively but shows moderation in his doings (see Knechtges, p. 288-289). In the Li Ji 禮記 it is said

田不以禮, 曰暴天物. 天子不合圍, 諸侯不掩群.
To hunt without observing the rules (for hunting) was deemed cruelty to the creatures of Heaven. The son of Heaven did not entirely surround (the hunting ground); and a feudal prince did not take a (whole) herd by surprise.
(Tr. Legge)

Royal hunts were used to forge alliances with other states (G. Shelach-Lavi, The Archaeology of Early China, p. 223). The game captured was used for the sacrifices to the ancestors, I assume to inform them of the new alliance and to ask for their consent:

The hunt, as recorded in bone inscriptions, is first and foremostly the prerogative of the king. It was not just a royal sport but rather a symbolic undertaking, that led to royal sacrifice and guaranteed the king’s role as supreme religious and political leader. Hunted animals were not buried or offered in sacrifice outside the ancestor cult. The primary purpose of hunting was thus not only to legitimize the king’s power but to provide sacrifice in maintaining the blessing of royal ancestor spirits.
E. Childs-Johnson, The Metamorphic Image: A Predominant Theme in the Ritual Art of Shang China, BMFEA 70, p. 38

There is another expression with the same pronunciation that is said to have the meaning of san qu 三驅, ‘three times drive/expel’. The Zuozhuan contains an unknown text that is said to be from hexagram 18 in the Yijing:

千乘三去,
三去之餘,
獲其雄狐.

James Legge translates this as

The thousand chariots thrice are put to flight,
What then remains you catch,
– the one fox wight
(Zuozhuan, p. 167)

Richard Rutt renders it as

A thousand cars thrice turn in flocks;
And when three times they’ve fled your shocks
Your prize will be a poxy fox
(Zhouyi, p. 180)

But this meaning does not fit the context of the line text of H8-5.

It is tempting to see the meaning of ‘three-sided hunt’ in the composition of the character qu 驅. This character consists of ma 馬 ‘horses’ and qu ‘區’. The latter evokes the picture of a three -sided round-up and the ‘horses’ component shows they used horses to do it. However this reading is not in any way substantiated by etymological studies of the character.

It is important to recognize the sanqu as a ceremonial procedure and not as an ordinary hunt. The ceremonial meaning will explain the 邑人不誡 part in the line text.

Shi 失: (let) escape; ignore.

Qian 前: the front, in the front.

Qin 禽: general name for animals, beasts.

Yiren 邑人: the (common) people.

According to the Great Dictionary of Chinese History (Zhongguo Lishi Da Cidian 中国历史大辞典) it is a title for a government position during the Shang and Zhou dynasty. As an example for an oracle bone inscription where yiren has this meaning it cites Heji #799 (see image on the right; click to enlarge). However, Qiu Xigui 裘錫圭 reads yiren in this inscription as ‘cityfolk’:

癸酉卜，王貞，自今癸酉至於乙酉，邑人見其方卬不見其方執。
Crack on guiyou, the king divining: From today guiyou reaching until yiyou, will the cityfolk see the borderlanders, or will (they) not see the borderlanders?
– Qiu Xigui, An Examination of Whether The Charges in Shang Oracle-Bone Inscriptions are Questions, Early China 14 (1989), p. 82

In bronze inscriptions yiren often refers to the people of Yi (Li Feng, “Offices” in Bronze Inscriptions and Western Zhou Government Administration, Early China Vol. 26/27 (2001–2002), pp. 1-72 ). But in most texts yiren refers to the common people, or the people in general:

天有邑人，何用弗愛也？
(So if) Heaven does possess the people, how could it be that it does not love them?
– Tr. I Johnston, The Mozi – A Complete Translation, p. 241

More specifically yiren might refer to people within a settlement or city, different from nomadic tribes. The 漢語大詞典 reads it as people from a feudal state.

Bu jie 不誡: not cautious, not suspicious; reassured, at ease. Because of the sanqu ceremonial hunt that shows the benevolent nature of the king the people of the new alliance are reassured. This line seems to talk of a realized bonding, effectuated by a joined hunt in which the king shows his benevolent attitude towards the other party. The yiren 邑人 might refer to the people of the other party.

Manifested alliance.
The king performs a sanqu and lets the game at the front escape.
The people (of the new ally) are reassured.
No curse from the ancestors.