The phrase a reed shaken in the wind
is a proverb (see 1 Kings 14:15) referring to a fickle, self-indulgent person. Jesus here means that John, unlike that, is steadfast, and, even in the midst of such difficulties as being imprisoned and his own ignorance, stays faithful to Jesus. John thus was not a coward, nor someone who had grown soft. He had stayed firm in conflict with Herod and the Jewish leaders.
The phrase a reed shaken in the wind
is a proverb (see also 1 Kings 14:15) and refers to someone who is both fickle and self-indulgent. Because the question demands a negative answer, Jesus here means to say that John is a steadfast man, who, even in the midst of difficulties such as being imprisoned and his own ignorance, remains faithful to him.1
Matthew 11:7b therefore first explains who John was not: he was not a coward, nor was he a person who had grown soft. His brave and steadfast stance in opposition to the Jewish leaders and Herod make this much clear.2
7 As they went away, Jesus began to speak to the crowds concerning John: “What did you go out into the wilderness to see? A reed shaken by the wind?