Jesus compared the members of the human body to the agents of sinful activities. He did not want His disciples to perform physical surgery but spiritual surgery to excise the sin within us. The language is hyperbolic, but Jesus described real sins. The threefold repetition highlights the importance of the warning (cf. Romans 6:12-13). [source][source][source]
"It was not a Palestinian custom to refer to an abstract activity but to the specific member of the body which is responsible for it. For this reason Jesus speaks of the offending hand, foot and eye, all members which have highly important functions to fulfill." [1][source]
"As a surgeon does not hesitate to cut off a gangrenous hand to save a life, so evil and destructive practices, though precious to us as a very part of our lives, must be sacrificed to save the soul [2]." [2]7 [source]
"Hell" translates the Greek word gehenna, the transliteration of the Hebrew phrase ge hinnom (lit. "Valley of Hinnom"). This valley, just south of Jerusalem, is where apostate Jews formerly offered human sacrifices to the pagan god Molech (cf. Jeremiah 7:31; Jeremiah 19:5-6; Jeremiah 32:35). King Josiah terminated this practice and converted the site into a city dump where rubbish burned constantly ( 2 Kings 23:10). The fire never went out at gehenna and the worms that fed on the garbage never died. Unquenchable fire must be eternal. [4] External fire and internal worms are Old Testament pictures of destruction (cf. Isaiah 66:24). Thus gehenna became a picture of the place of eternal punishment (Enoch27:2; 90:26), not annihilation. [5] The word gehenna appears12times in the New Testament, and in all but one of these occurrences Jesus spoke it (i.e, James 3:6). [source][source][source]
Disciples should take prompt and decisive action against anything that might lead them away from their allegiance to Jesus. Physical temptations come through the hands (what we do), the feet (where we go), and the eyes (what we see) primarily. Disciples who are believers will suffer the loss of rewards in the kingdom if they do not exercise self-discipline. Disciples who are unbelievers will experience eternal damnation if they fail to do so. [source][source][source]Mark 9:44; Mark 9:46 are absent in important early manuscripts. Probably scribes added them later to fill out the parallelism in the passage. They repeat Mark 9:48. [source][source][source]