Yaakov is haunted by doubts. He has left the Land as a fugitive, fleeing in fear of his brother's vengeance; now he returns as a rich family man, to claim the firstborn rights he has bought. But is it so?
"Yaakov remained alone; and a man wrestled with him until daybreak" (32;25)
Rashi, and most of the commentators, follow the translation of Menachem (one of the first Hebrew linguists), which translated "Va'Ye'avek" (wrestled) as coming from "Avak" (dust). Yaakov actually wrestles with this man, in a mortal combat. In the end he emerges the victor - pinning down his opponent, and receiving a blessing from him. He is injured in the struggle, and sprains his thigh - but still has his foe at his mercy. After letting him go, he limps past Pnu'el as the sun rises (32;32). But the sun is a healing sun, and he recovers (Bereishit Rabba 78;4, quoted in Rashi) - as the sun in the final day of the Lord will heal the righteous (Mal'achi 3;20). Yaakov more than recovers his physical health - he catches a glimpse of the end of days, something worth passing to his sons after him (49;1. According to the Gemara in Pesakhim 56a, he was denied the privilege of telling them).
Chazal (Bereishit Rabba 77;3) identify the mysterious adversary as Esau's guardian angel, raising the level of the rivalry between the twin brothers to a metaphysical conflict. This explains Yaakov insisting on being blessed by him - but is quite incomprehensible: how could a purely spiritual being, interlock in a physical combat with a mortal man?
Radak suggests the whole struggle took place in a prophetic dream, and Yaakov's lameness was a separate miracle, affirming the vision. Even he accepts the standard interpretation; but Rambam (More Nevuchim 2;42) is adamant in rejecting it, and sticks to the vision explanation.
Ramban follows Rashi, but notes that Onkelos translated "Va'Ye'avek" to a more neutral word, signifying "quarreled" or even "argued". This reading may support Rambam's reading.
In Chulin 91a, the Gemara brings two opinions. According to Rav Shmuel bar Nachmani, the angel appeared to Yaakov as a gentile (in Bereishit Rabba 77;2 - as a robber); according to Rav Shmuel bar Acha - as a talmid-chacham. If we accept the second opinion, this is not just a fair disguise to foul intentions; it projects the struggle into an intellectual, spiritual sphere.
Yaakov is haunted by doubts. He has left the Land as a fugitive, fleeing in fear of his brother's vengeance; now he returns as a rich family man, to claim the firstborn rights he has bought. But is it so? The right he had bought by taking advantage of a simple, starving brother; and the blessings he received by deceiving his blind father, aided by the eavesdropping of a loving mother. Esau may be a murderous villain, and totally unworthy of either - but is Yaakov better than a common swindler?
Before returning home, Yaakov must be sure of himself. He must clear himself of any stain a sensitive conscience may feel, and of any claim Esau may have upon him. So he fights to the end, until he is blessed by Esau's guardian angel - thus attaining the needed recognition of his right to the blessings (Rashi on 32;27). And even though he is maimed in the process, he is healed by a merciful sun - a foretaste of the days to come, reassuring him that he is the firstborn of the Lord (Shemot 4;22).
This struggle could not take place before. Before, Yaakov was ever active. He had to send the present to appease his injured brother, to pray, and to prepare for war (Rashi on 32;9). But now, in the last night before the long-feared confrontation, when he remains alone, the doubts settle in. Alone, he confronts the spiritual claims of Esau - without his family, and without any guardian angel of his own. And alone, he wrestles to the bitter end - until daybreak.