Jeremiah expresses his confusion as he compares himself to a gentle lamb led to the slaughter.
The emphasis seems to be on the fact that, just like a lamb does not know what is happening when taken to be slaughtered, so Jeremiah did not know what was happening to him. I did not know it was against me they devised schemes.
19 J'étais comme un agneau familier qu'on mène à la boucherie, Et j'ignorais les mauvais desseins qu'ils méditaient contre moi: Détruisons l'arbre avec son fruit! Retranchons-le de la terre des vivants, Et qu'on ne se souvienne plus de son nom!