Behold their sitting down, and their rising up; I am their musick.

Wesley's Notes

3:63 I am - At feasts, and at their merry meetings, I am all the subject of their discourse.

Jamieson-Fausset-Brown Bible Commentary

63. sitting down . rising up-whether they sit or rise, that is, whether they be actively engaged or sedentary, and at rest "all the day" (La 3:62), I am the subject of their derisive songs (La 3:14).

Tau.

Matthew Henry's Concise Commentary

3:55-66 Faith comes off conqueror, for in these verses the prophet concludes with some comfort. Prayer is the breath of the new man, drawing in the air of mercy in petitions, and returning it in praises; it proves and maintains the spiritual life. He silenced their fears, and quieted their spirits. Thou saidst, Fear not. This was the language of God's grace, by the witness of his Spirit with their spirits. And what are all our sorrows, compared with those of the Redeemer? He will deliver his people from every trouble, and revive his church from every persecution. He will save believers with everlasting salvation, while his enemies perish with everlasting destruction.