Markus 9:42

9:42 “If anyone causes one of these little ones who believe in me to sin, it would be better for him to have a huge millstone ¹  tied around his neck and to be thrown into the sea.

Lukas 17:2

17:2 It would be better for him to have a millstone ²  tied around his neck and be thrown into the sea ³  than for him to cause one of these little ones to sin. ⁴ 

[9:42]  ¹ tn Grk “the millstone of a donkey.” This refers to a large flat stone turned by a donkey in the process of grinding grain (BDAG 661 s.v. μύλος 2; L&N 7.68-69). The same term is used in the parallel account in Matt 18:6.

[9:42]  sn The punishment of drowning with a heavy weight attached is extremely gruesome and reflects Jesus’ views concerning those who cause others who believe in him to sin.

[17:2]  ² tn This term refers to the heavy upper stone of a grinding mill (L&N 7.70; BDAG 660 s.v. μυλικός).

[17:2]  sn The punishment of drowning with a heavy weight attached is extremely gruesome and reflects Jesus’ views concerning those who cause others who believe in him to sin.

[17:2]  ³ tn Grk “if a millstone were tied…and he were thrown.” The conditional construction in Greek has been translated by English infinitives: “to have… and be thrown.”

[17:2]  ⁴ tn Or “to stumble.” This verb, σκανδαλίσῃ (skandalish), has the same root as the noun σκάνδαλον (skandalon) in 17:1, translated “stumbling blocks”; this wordplay is difficult to reproduce in English. It is possible that the primary cause of offense here would be leading disciples (“little ones”) astray in a similar fashion.