Musar su Salmi 1:1

King David began the book of Tehillim with the words, “Fortunate is the man who has not walked in the counsil of the wicked … nor did he sit in a gathering of scoffers” (1:1). Similarly, our Rabbis have said in Pirkei Avos, “When two people sit together and there are no words of Torah between them, it is a ‘gathering of scoffers’” (3:2). Since, on account of our many sins, this is a very common circumstance a person must pay careful heed to this warning. Whenever he sits with his companions he must be certain that the discussion consists of words of Torah or character development or awe of Heaven. It goes without saying that he must avoid the company of scoffers and idlers who sit together engaging in frivolity. For in the course of their endless chatter they inevitably come to utter words of mockery and derogatory speech, thereby giving rise to harmful forces that inflict damage upon their souls. Therefore whoever fears the word of Hashem will distance himself from such company.

This is the intent of Shlomo's warning: "do not mingle with those who make changes" (Prov.24:21). If a man claims to you: "a person's mind should always be associated with his fellow men" (Ketuvot 17a), reply to him, "this refers to human beings who act like human beings. Not human beings who act like animals." Shlomo warns further: "Go from before a foolish man" (Prov. 14:7). And King David said: "Fortunate is the man that walks not in the counsel of the wicked, nor stands in the way of sinners, nor sits in the seat of scoffers" (Ps. 1:1). Our sages expounded this: "If he walks, he will eventually stand. If he stood, he will eventually sit" (Avodah Zara 18b). And "I did not sit with men of falsehood, neither did I go with hypocrites. I have hated the congregation of evil-doers, and will not sit with the wicked" (Ps. 26:4-5).

"it was all grown over with thorns" - refers to one who seeks the interpretation of a portion of the Torah and does not find it.