Eliezer's bittul to the tzaddik's will

ברש"י אלי כתיב כו'.

In Rashi: "elai" ("to me") is written [defectively], etc.

Rashi notes that when Eliezer retells his mission, the word "to me" is spelled in a way that hints at his own personal stake in the matter — for he had a daughter he might have wished Yitzchak to marry.

כי בודאי אליעזר עשה השליחות בכוונה רצוי' שהרי הצליח בשליחותו.

For certainly Eliezer carried out the shlichus (mission) with proper intention, since he succeeded in his mission.

The very fact that Eliezer's mission was crowned with success proves that he acted with pure and proper kavanah on behalf of Avraham.

אעפ"י שהי' נוגע במה שרצה להשיאו לבתו.

Even though he had a personal interest, for he had wished to marry off his own daughter to him.

Despite his private hope that Yitzchak would marry Eliezer's own daughter — a genuine personal bias — it did not corrupt his service.

אעפ"כ ביטל עצמו בעבור רצון הצדיק.

Even so, he nullified himself (bittul) for the sake of the will of the tzaddik.

Eliezer achieved complete bittul, setting aside his own desire entirely in deference to the ratzon of Avraham, the tzaddik he served.

וי"ל שזה עצמו סיפר להם שלא יעכבו הדבר באשר שגם הוא נוגע בדבר ואעפ"כ מבטל רצונו כנ"ל:

And one may say that this itself is what he told them — so that they should not delay the matter — namely, that he too had a personal interest in the matter, and yet he nullifies his own will, as above.

Eliezer deliberately disclosed his own bias to Lavan and Besuel as an argument: if even he, who stood to gain, set aside his will before the tzaddik's, then surely they should not hold up the shidduch.

Summary: The defective spelling of "elai" reveals Eliezer's personal stake in Yitzchak's marriage. Yet his success shows he served with pure intention, achieving bittul by surrendering his own desire to the will of Avraham the tzaddik — and he openly told this to Rivkah's family so they would not delay the match.