אבן העזר קי״טEven HaEzer 119

Se’if 1א׳

לֹא יִשָּׂא אָדָם אִשָּׁה וְדַעְתּוֹ לְגָרְשָׁהּ. וְאִם הוֹדִיעָהּ בִּתְחִלָּה שֶׁהוּא נוֹשֵׂא אוֹתָהּ לְיָמִים, מֻתָּר:

One may not marry a woman who he intends to divorce. However, if he indicates to her in advance that he's marrying her for a fixed period of time, he is permitted to.

Se’if 2ב׳

לֹא תִּהְיֶה יוֹשֶׁבֶת תַּחְתָּיו וּמְשַׁמַּשְׁתּוֹ, וְדַעְתּוֹ לְגָרְשָׁהּ:

She may not live with him and serve him when he intends to divorce her.

Se’if 3ג׳

לֹא יְגָרֵשׁ אָדָם אִשְׁתּוֹ רִאשׁוֹנָה, אֶלָּא אִם כֵּן מָצָא בָּהּ עֶרְוַת דָּבָר. הַגָּה: אֲבָל בְּלָאו הָכִי אָמְרִינָן כָּל הַמְגָרֵשׁ אִשְׁתּוֹ רִאשׁוֹנָה מִזְבֵּחַ מוֹרִיד עָלָיו דְּמָעוֹת (טוּר). וְדַוְקָא בִּימֵיהֶם שֶׁהָיוּ מְגָרְשִׁין בְּעַל כָּרְחָהּ, אֲבָל אִם מְגָרְשָׁהּ מִדַּעְתָּהּ מֻתָּר (אֲגֻדָּה פֶּרֶק הַמְגָרֵשׁ וְכֵן כָּתַב הָרַ"ן). וְאֵין רָאוּי לוֹ לְמַהֵר לְשַׁלֵּחַ אִשְׁתּוֹ רִאשׁוֹנָה; אֲבָל שְׁנִיָּה, אִם שְׂנָאָהּ, יְשַׁלְּחֶנָּה:

One should not divorce his first wife unless he found something unseemly about her. hagah: Aside from this, the rabbis said: "if someone divorces his first wife, the alter cries tears upon him". This is specifically talking in their days (time of the talmud), when they frequently divorced a woman even against her will (this is when the alter cries). but if she consents it is permitted. You should try to not rush into divorcing your first wife, but the second wife, if you dislike her, you can divorce her.