Adam Clarke on Jeremiah 34:5

Thou shalt die in peace - Thou shalt not die a violent death; and at thy death thou shalt have all those funereal solemnities which were usual at the demise of kings. See 2Chr 16:14.

So shall they burn odours for thee - Scented wood and other odoriferous substances are placed on the funeral pile of the rich Hindoos, and burned with the body.

And they will lament thee, saying, Ah lord! - They will recite the funeral dirge that begins with those words. See the note on Jer 22:18 (note).