Why did he walk in the house?
Radak: He returned to the ground to pray. After he ascended on the bed and the boy's body warmed, he returned to the ground, prayed, and fell on the body again. He went to different places to increase intent - "Es'halech b'Sam Levavi b'Kerev Beisi" (Tehilim 101:2).
What is the meaning of "va'Yzorer"?
Rashi: He sneezed. Radak - the Targum of "Atishosav Tahel Or" (Iyov 41:10) is Zerizohi.
Mahari Kara: He stretched his arms.
What happened seven times?
Metzudas David: The boy sneezed seven times.
Malbim: Elisha descended to pray, and returned to lie on the boy. This was (a) to draw endurance to his body below for the 70 years of his (i.e. an average) lifetime; a person's nature changes seven times. 1 (b) To draw influence from above for the seven days of upper building 2 .
Avos 5:21 lists changes in a man that occur after each 10 years. Perhaps 'at 13 he is obligated in Mitzvos' and 'at 18 he should marry' do not count, for these are not changes in his nature. Perhaps nothing the latter is not due to a change, rather, he should seek a wife then, to ensure that he marry before 20, when his nature changes. However, the Yetzer Tov enters at 13. Is there a change greater than this?! (PF)
This is a Kabalistic concept.
