How did Lavan's words counter Yakov's claim?
Rashi and Rashbam 1 : He was stating that it would not even enter his mind to harm any of all those mentioned in the Pasuk.
Seforno: He maintained that, even assuming that he did switch the conditions, or send him away empty-handed, he would have been acting within his rights, seeing as everything that Yakov owned, he obtained by trickery. Indeed, he added, he (Lavan) was perfectly entitled to take them all. 2
Ramban: He pointed out that he could not possibly harm his own daughters and their children, who were born in his home. And he claimed that he had run after him, not to do them harm, but to see what good he could do on their behalf.
Oznayim la'Torah: In answer to Yakov's claim "Mah Matzasa mi'Kol K'lei Beisecha"? the girls, the sons, the sheep and everything that Yakov has belongs to him; and in answer to "Ki Amarti 'Pen Tigzol es Benosecha", he pointed out that he loved his daughters and their children dearly and would never do them harm.
Why did Lavan add the word "l'Eileh" (to these)?
Redak: To daughters as good as these, how could I do anything [bad]?!
How can Lavan say that everything is his? He himself (Bereishis 30:27) said that Hashem blessed him due to Yakov!
Ohr Yechezkel Midos p.15-16: This shows what lowliness is possible in a person.
How can Lavan say "the sons are mine"? Yakov fathered them!
Moshav Zekenim: He said that Yakov is an Eved Ivri, so "ha'Ishah vi'Yladeha Tihyeh la'Doneha." 1
He could say so about Bnei Bilhah and Zilpah, who were slaves. What is his claim to Bnei Leah and Rachel?! (PF)
Why did Lavan say "what can I do to these today"?
Tosfos ha'Shalem (6, citing R. Efrayim): Had I known you were leaving, I would have given to them pillows, blankets and household Kelim. Here, I have nothing to give to them.
משמעות הפסוק שאלמלא נגלה ה' אל לבן לא היה מחשיב את הבנים לבניו והבנות לבנותיו- אלא הוא רצה לעקור את הכל, וצריך ביאור למה שנא לבן את יעקב?
מהר"ל (גבורות ה', פנ"ד, עמ' רלז, ד"ה צא): לבן שנא את יעקב בלי סיבה מפני שהם הפכים זה לזה- יעקב הוא המציאות ואילו על הארמיים כתוב שהקב"ה מתחרט שבראם, כלומר שלא ראויה להם המציאות מצד עצמם אלא כטפלים לנבראים אחרים. 1
עי' עוד בגור אריה (דברים לב, כא) שביאר שהם לא ממניין שבעים אומות.
רש"י: איך תעלה על לבי להרע להן: למה פירש רש"י "מה" מלשון 'איך'?
גור אריה: לבן לא היה מסופק מה לעשות להם, ולכן יש לפרש "מה אעשה להם" שאין להעלות על הדעת שהוא יעשה להם רע.