As per Mahabharata: Adi Parva: Swayamvara Parva: Section CLXLIII, the intelligent king (Yudhishthira) told Dhananjaya,
'By thee, O Phalguna, hath Yajnaseni been won. It is proper, therefore, that thou shouldst wed her. O thou withstander of all foes, igniting the sacred fire, take thou her hand with due rites.'
Arjuna, hearing this, replied,
O king, do not make me a participator in sin. Thy behest is not conformable to virtue. That is the path followed by the sinful. Thou shouldst wed first, then the strong-armed Bhima of inconceivable feats, then myself,...
But, Bhima was already married to Hidimva by that time. So what does that mean?
And why this point was not raised when Bhima got married to Hidimva that he should not get married before Yudhisthira?
Later, Yudhishthir also says similar things
I am unmarried still, and Bhima also is so amongst the sons of Pandu. ~ Did Kunti explicitly told Pandavas to marry Draupadi?