We - The form used here occurs nowhere else in the Old Testament, but is the regular form of the pronoun in the Talmud. It is one out of many instances of Jeremiah using the popular instead of the literary language of his times.
Matthew Henry
Concise Bible Commentary
To serve a turn, Jeremiah is sought out, and the captains ask for his assistance. In every difficult, doubtful case, we must look to God for direction; and we may still, in faith, pray to be guided by a spirit of wisdom in our hearts, and the leadings of Providence. We do not truly desire to know the mind of God, if we do not fully resolve to comply with it when we know it. Many promise to do what the Lord requires, while they hope to have their pride flattered, and their favourite lusts spared. Yet something betrays the state of their hearts.
SDA Bible Commentary (limited)
Volume 1-7
7. After ten days. This time lapse should have been an evidence to the people that Jeremiah was not giving his own answer but one that came through him from God after much prayer and meditation (see on Jer. 24:4; cf.Eze. 3:15, 16).