The reversals in Mark’s Gospel are fascinating. Throughout Mark 2, the Pharisees and scribes are checking Jesus out, scrutinizing his conduct in light of their own conceptions of Law-observance.
They query Jesus as to his eating with sinners (2:16) and his disciples’ conduct on the Sabbath (2:24). By Mark 3:1-6, however, they find themselves plotting evil on the Sabbath.
The motives and behavior of these self-appointed watchdogs reveal the truth:
The Pharisees are described as “watching closely” (paretēroun) to see if Jesus will heal on the Sabbath. This same verb is used in Ps 36:12 (one of only two LXX usages), where it is sinners who lie in wait for the righteous person to slay him (cf. Ps 129:3) – a portrayal similar to the description of the Pharisees’ plot at the end of our passage (3:6). Through the intertextual echo with Psalm 36, then, the same Pharisees who have objected to Jesus’ eating with “sinners” (2:16) are now revealed to belong in the camp of sinners themselves.
Joel Marcus, Mark 1-8, 252.