What did Rachel mean when she called Bilhah's second son Naftali because "Naftulei Elokim Niftalti ... "?
Rashia and Rashbam: Based on the word 'Pasil', she meant that she had joined with her sister 1 to merit children.
Seforno: She meant that she was intimately joined with her husband with a Divine and holy union, because, together with her sister, she gave her maidservant to her husband in order to bear the tribes of Yisrael. 2
Targum Onkelos: She beseeched Hashem in prayer, and He answered her, and gave her a child, like her sister.
Da'as Zekenim: She suffered great pain.
Tosfos ha'Shalem (5): I strove to overcome her, and I succeeded.
Tosfos ha'Shalem (9): I was crooked with Simanim (ha'Chosemes and Pesilim were Simanim) with my sister [to help her fool Yakov], and succeeded. A Midrash says that when Yakov married Leah, Rachel was under the bed, and when Yakov called "Rachel", she answered.
Da'as Zekenim, Hadar Zekenim: She joined her regarding skilled descendants. Ohali'av from Dan helped Betzalel [from Yehudah] to build the Mishkan, and Chiram from Naftoli helped Shlomo [from Yehudah] to build Bayis Rishon.
Because Le'ah must have given Zilpah to Yakov before the birth of Naftali (See Seforno).
And what did she mean when she added "Gam Yacholti"?
Seforno: She meant that, with the birth of Bilhah's children, she had achieved what she set out to do by giving Bilhah to Yakov.
Da'as Zekenim, Moshav Zekenim, Rosh: This implies that she exceeded Leah! One Chacham builder will come from Leah (Betzalel), and two from Bilhah - Ohali'av from Dan, and Chiram (who finished Bayis Rishon) from Naftoli.
Le'ah has four sons and she has not even one!How can she say "Niftalti im Achosi Gam Yacholti!"?
Oznayim la'Torah: Rachel figured that, since Le'ah had stopped giving birth, and Bilhah already had two sons, Bilhah would give birth to another two sons - four like Le'ah. Leaving her to produce the remaining four, 1 thereby giving her the edge over Le'ah.