Both of these phrases say the same thing for emphasis. Jacob uses the words "soul" and "heart" to refer to himself. AT: "I certainly will not join with them to make any plans" (See: [[rc://en/ta/man/translate/figs-parallelism]])
## My self...my heart ##
Jacob uses the words "self" and "heart" to refer to the most noble parts of himself.
## they hamstrung oxen ##
Jacob compares the men of Shechem to oxen. This emphasizes the strength of the men and that Simenon and Levi killed them as if the men were just animals. AT: "they slaughtered men like they slaughter oxen" (See: [[rc://en/ta/man/translate/figs-metaphor]])