Why did Yaakov find it necessary to exert himself and sit up on the bed when Yosef arrived?
Rashi and Seforno: Because effectively, Yosef was a king, and one is obligated to honor a king. 1
Rashbam: He actually sat on the bed with his feet on the ground. 2
Moshav Zekenim: He wanted to show that he is healthy, lest people say that his mind was befuddled, so his gift is invalid. 3
Ha'amek Davar: He prepared himself for his level [of Ru'ach ha'Kodesh, indicated by the name Yisrael used here. Refer to 48:2:151:1].
Moshe, when he honored Pharaoh (See Shemos 11:8) and Eliyahu, when he honored Ach'av (see Melachim I 18:46) took their cue from Yaakov.
The Rashbam says this (not to answer the question, but) in order to explain how he removed the boys from on his knees (48:12).
Da'as Zekenim and Hadar Zekenim: Lest people say that it was 'Matenas Shechiv Mera' (which is valid, but the giver can retract); and to show his mind was settled.
Why does it say "va'Yaged"?
Ha'amek Davar: He told Yaakov that Yosef is not coming for a mere visit. Rather, he is bringing his sons, and hopes to receive a special Berachah at this time. Therefore, Yaakov should prepare himself for Ru'ach ha'Kodesh. In Egypt, he did not always have Ru'ach ha'Kodesh, but when needed, he prepared himself for it, and received like a lightning bolt that illuminates the night. All the more so when he is ill, he is more apt to reach his level, like a lamp that burns brightly just before it extinguishes.
