Jamieson, Fausset and Brown on Daniel 4:27

27. break off--as a galling yoke (Ge 27:40); sin is a heavy load (Mt 11:28). The Septuagint and Vulgate translate not so well, "redeem," which is made an argument for Rome's doctrine of the expiation of sins by meritorious works. Even translate it so, it can only mean; Repent and show the reality of thy repentance by works of justice and charity (compare Lu 11:41); so God will remit thy punishment. The trouble will be longer before it comes, or shorter when it does come. Compare the cases of Hezekiah, Is 38:1-5; Nineveh, Jon 3:5-10; Jr 18:7, 8. The change is not in God, but in the sinner who repents. As the king who had provoked God's judgments by sin, so he might avert it by a return to righteousness (compare Psa 41:1, 2; Ac 8:22). Probably, like most Oriental despots, Nebuchadnezzar had oppressed the poor by forcing them to labor in his great public works without adequate remuneration.

if ... lengthening of ... tranquillity--if haply thy present prosperity shall be prolonged.