Midrasch zu Könige I 14:15

R. Samuel b. Nachmeni in the name of R. Jonathan said: "What is the meaning of (Prov. 27, 6) Faithful are the wounds of a friend; but the kisses of an enemy are importune, i.e. The caution that Achiyah the Shilonite cautioned Israel is better for them than the blessings that Bil'am blessed them. The former cautioned Israel giving as a simile the reed, as it is said (I Kings 14, 15) As the reed is shaken in the water. As this reed stands in water-places, the branches (Fol. 106) of it change, but its roots are many, and even all the winds of the world when blowing upon it are not able to uproot it, but it bends in every direction of the wind. However, when the wind ceases it remains straight in its place. But Bil'am, the wicked, blessed Israel likening them to a cedar, which does not stand in waterplaces, does not change its branches, and its roots are few, and although no winds can affect it, however, as soon as a south wind comes it uproots it and turns it over on its face. Moreover, a pen for writing the Holy Scrolls, the Prophets and the Hagiographa is made from a reed."