Why is the word "Ulai" missing a 'Vav'?
Rashi: Without a 'Vav' it can be read 'Elai' (to me). This tells us that Eliezer had a daughter whom he hoped Yitzchak would marry. 1
Refer to 24:39:152:4.
Rashi said that Eliezer hoped that Yitzchak would marry his daughter. On what grounds did Avraham not consider it?
How does Rashi learn from Ulai that Eliezer hoped that Yitzchak would marry his daughter? Ulai is the same with or without the Vav. Eliezer needed to ask what to do if she does not want to come!
Divrei Eliyahu, Kol Eliyahu: One says "Pen" 1 for a possibility he does not want to occur, and "Ulai" if he wants it to occur. 2 Why would Eliezer want that she will not want to come, if not that he had a daughter... 3
Malbim (Yehoshua 9:7) says that Ulai implies that this probably is the case. Perhaps it is written Chaser to hint that this was not true. Eliezer said due to his bias (his hope that she will not want to come, and his daughter can marry Yitzchak). (PF)
Normally, "Pen" follows an action that should not be done, but there are exceptions, e.g. Devarim 19:6, 29:17. Also here, it could have said "Pen", had Eliezer wanted that she want to come!
The Magihah in Kol Eliyahu resolves three seeming exceptions to this rule. Refer to 27:12:151:1, refer to 50:15:151:1. (Yisrael said to the Giv'onim (Yehoshua 9:7) "Ulai b'Kirbi Atah Yoshev"! Perhaps they hoped so, for then they can demand taxes and servitude from them (refer to Yehoshua 9:21:2:1.
Why is "Ulai" here missing a 'Vav', but above (Pasuk 5) it has a Vav?
Moshav Zekenim: Only now that he ceased to be cursed (refer to 24:31:1:2), he thought that his daughter is proper for Yitzchak.
Lev Eliyahu (Bereishis p.79): Now, after he ceased to be cursed, he realized his intent.
The Kotzker Rebbe (brought in Lev Eliyahu Bereishis p.79, b'Hagahah): After he saw that Rivkah is destined for Yitzchak, his bias departed, and retroactively he recognized his intent.
Ha'Emek Davar: Here, Eliezer hinted to her family that it is unlikely that she will not want to go, so they will understand that it is good for them.
Eliezer asked Avraham 'if she will not want (a) to follow me (b) to this land.' Why did he tell them only the first?
Malbim: He wanted them to understand that if even if she wants to go to Eretz Yisrael, just she does not want to go with a slave, he is exempt from the oath.
Avraham had said (verse 7) "Hashem took me and my seed from there." Why did Eliezer omit this?
Malbim: It implies that Avraham despised his birthplace. This is unlike his claim that Avraham wants a girl from his family.