John Paul Heil, «A Note on Elijah with Moses in Mark 9,4», Vol. 80 (1999) 115-115
Whereas Matt 17,3 and Luke 9,30 mention Moses first and coordinate him with Elijah in the expression, "Moses and (kai\) Elijah", Mark 9,4 mentions Elijah first and seems to subordinate Moses to him in the expression, "Elijah with (su\n) Moses" 1. But a close examination of all the instances where Mark uses the preposition su/n indicates that this is not the case. On the contrary, the object of the preposition su\n in every instance represents the more notable party.
In Mark 2,26 the preposition su/n subordinates the members of David's army to him as their superior; they were allowed to eat the bread of the presence simply because they were "those who were with him" (toi=j su\n au)tw=| ou]sin), David, their leader. In 4,10 su/n subordinates "those around Jesus" to "the Twelve," the specially chosen elite sub-group of disciples (3,14). That "those around him" are "with the Twelve" (su\n dw/deka ) enhances the stature of this grouping for the contrast to "those outside" (4,11) 2. In 8,34 su/n subordinates "the crowd" to "the disciples," the more prominent party. Jesus called "the crowd with his disciples (su\n toi=j maqhtai=j au/tou=)" in order to address his command to take up the cross and follow him especially to the disciples, who, despite already following him (8,33), do not understand the necessity for his suffering (8,31-32) 3. In 15,27 and 15,32 su/n subordinates the two robbers crucified "with him" (su\n au)tw=| ) to Jesus, the chief character in the narrative.
Especially revelant here are Mark 4,10 and 8,34. They demonstrate how for Mark the party mentioned second and introduced with su/n actually enhances the grouping. The party added to a grouping with a su/n stands out for special emphasis: "those around him with (su\n), that is, including even and especially, the Twelve" (4,10) and "the crowd with (su\n), that is, including even and especially, his disciples" (8,34). Rather than subordinating Moses to Elijah, then, Mark 9,4 actually emphasizes the addition of Moses as enhancing their coupling. Thus, we might paraphrase this special use of su/n in Mark 9,4 as follows: "Then there appeared to them Elijah with (su\n), that is, including even, Moses" not only Elijah but even Moses! Hence Mark says basically the same as Matt 17,3 and Luke 9,30 here but with slightly more emphasis upon Moses as even more notable than Elijah 4.