'Rashi' (Divrei ha'Yamim II, 10:4): He imposed on us to feed his workers and pay a tax (Melachim I, 5:27).

Radak: He put a tax on them every year. Even so, they should not have complained, for there was great serenity in his days, and the tax was light on them, for an enemy did not come on them in his days. Rather, Hashem caused them to seek a pretext against Rechav'am, so they will separate and declare Yaravam king.

Malbim: A yoke is what forces an ox to work. It is a metaphor for one who rules with a strong hand and punishes severely one who transgresses his commands. There are two kinds of kingship. (a) A limited kingship, in which the king cannot do anything without the nation's consent and their chosen [leaders], and according to the country's laws. Also he cannot impose on them work and taxes without their consent. (b) An unlimited kingship, in which the king rules alone as he desires, and he can impose on them work and taxes as he wants, without asking their opinion, for they are all his slaves. He can force them to do his work via making the yoke heavy, i.e. he fixes harsh and bitter punishments for one who does not heed his voice. Initially, Malchus Yisrael in the days of David was limited. Shlomo strengthened to rule by himself an unlimited kingship. Therefore he put on them a harsh yoke that anyone who transgresses his mouth will be killed ¹ , even if he commands matters not good for the nation.

Malbim: Shlomo imposed a harsh yoke improperly; the laws of kingship did not entitle him. We needed to be silent to Shlomo, for he was already king, and we could not rebel against him. You are not king yet. You must be bound by the laws! (a) We will fix limits on how much you may tax and impose a yoke. (b) Your kingship will be limited, under people chosen by the nation and laws of the country.