Gemara

82a (Mishnah - R. Eliezer): If a man divorced his wife, and said 'you are permitted to any man, Ela (but not) to Ploni', she is permitted to all other men;

Chachamim say, she is (not divorced, and is) forbidden to all men. He must take the Get and give it again, and say 'you are permitted to all men.'

If he wrote it (the Tenai) in the Get, even if it was later erased, the Get is Pasul.

83b (Rava): If one said 'this is your Get Al Menas (on condition) that you do not drink wine for the rest of your life', it is not Krisus. (The Get is Batel.)

84b (Mishnah): If he wrote it in the Get, even if it was erased, the Get is Pasul.

(Rava): This is when the Tenai is after the Toref (their names and the date). If the Tenai precedes the Toref, even if it was not written in the Get, the Get is Pasul.

For this reason, Rava would silence the husband until the Toref was written.

(Beraisa - Rebbi): Any Tenai disqualifies a Get;

Chachamim say, only a Tenai that disqualifies a Get orally, disqualifies it when it is written in it: 'Except for Ploni', disqualifies orally, or if it is written. 'Al Menas that you don't marry Ploni' does not disqualify orally, nor if it is written.

(Rava): Rebbi and Chachamim argue about a Tenai after the Toref. Rebbi decrees to disqualify it due to a Tenai before the Toref. Chachamim do not decree. All agree that Tena'im before the Toref disqualify a Get.

Our Mishnah says that only written Tena'im disqualify, and only 'Chutz (except for)', but not 'Al Menas.' It discusses after the Toref. It is like Chachamim.

Rishonim

Rif and Rosh (9:3): Our Mishnah disqualifies only written Tena'im, and only Chutz, but not Al Menas. It discusses Tana'im after the Toref. It is like Chachamim.

Ran (DH v'Nimtza): The only Pesul mid'Oraisa is if Chutz was written before the Toref. A verbal Tenai of Chutz before the Toref, or a Tenai of Chutz written after, is Pasul mid'Rabanan. We do not decree about a verbal Tenai of Chutz after the Toref. A written Tenai of Al Menas before the Toref is Pasul mid'Rabanan. Some say so even if it was verbal. A Tenai of Al Menas after the Toref is not Posel if it was fulfilled or pardoned.

Rambam (Hilchos Gerushin 8:16): If one divorced with a Tenai that is Mevatel a Get, e.g. that she never drink wine her entire life, or she is permitted to all men except for Ploni, or other Tana'im before the Toref was written:

If the Tenai was written in the Get, and he erased it and gave it to her, she is Safek divorced. If the Tenai was verbal, he takes the Get from her and gives it again with a Kosher Tenai or without any Tenai.

Gra (EH 147:3): This is imprecise. If such a Tenai was before the Toref, the Get is Batel! A Tenai of except for Ploni is not "Krisus" (83a). Rava upheld this question, and a Beraisa supports him. After the Toref, the Get is Pasul only mid'Rabanan (if the Tenai was erased before the Get was given).

Magid Mishneh: If other Tana'im were after the Toref, the Get is Kosher if the Tenai was fulfilled.

Poskim

Shulchan Aruch (EH 147:2): If the Tenai was written before the Toref, even 'Al Menas so and so', it is Safek divorce, for he still has privileges in the Get.

Gra (3): The Rambam explains like Rashi and Tosfos (DH Shtuki), that we discuss all Tena'im. If a Tenai does not disqualify a Get, whether it was written or verbal, it is Posel only if it was before the Toref. A Tenai that is Mevatel a Get, e.g. 'all of your life' or 'except for Ploni', disqualified a Get if it was written even after the Toref. If it was verbal, it disqualifies only before the Toref. The Rambam did not discuss Tena'im (that are Mevatel Gitin) made verbally, for he equated all Tana'im. 'Tena'im that are Mevatel Gitin' are those that disqualify even at the time he gives the Get.

Beis Yosef (DH v'Garsinan): Rashi says that any Tenai written in a Get disqualifies it, even if it was fulfilled. The Ri (in Tosfos DH Kol) disagrees. Why should we decree about a Tenai such as giving 200 Zuz, due to a Tenai of Chutz? There is no remnant (to divorce) in other Tena'im, except for 'Al Menas that you will not marry Ploni.' The Ri explains that the Beraisa refers to the Mishnah, i.e. Tena'im of 'Chutz mi'Ploni' and 'Al Menas that you will not marry Ploni.' Rebbi decrees that erasing and nullifying the Tenai does not help. The Get is Pasul unless the Tenai was fulfilled. This is even for a Tenai of Al Menas, lest people think that erasing helps for 'except for Ploni.' (It does not, for the Get was not written for Kerisus.) Chachamim do not decree.

Beis Yosef (DH u'Mah she'Chosav she'Im...): Many Rishonim do not go so far to decree to disqualify a verbal Tenai of Al Menas, even before the Toref. The Rashba proves this from a Tosefta (4:7), which allows a Get written Al Menas that she wait two years for him. However, nowadays we do not mention any Tenai before the Get is written, for not all know to distinguish between different Tena'im, and between before and after the Toref.

Beis Yosef (DH ul'Inyan Mah): Many say that letter of the law, only 'Chutz' written before the Toref disqualifies. Everything else is only a decree due to this. Some say that letter of the law, also 'Chutz' verbally before the Toref is Pasul.

Shulchan Aruch (3): If one divorced with a Tenai that is Mevatel a Get, e.g. that she not eat meat or drink wine her entire life, or she is permitted to all men Chutz mi'Ploni, or other Tana'im before the Toref was written:

If the Tenai was written in the Get, and he erased it and gave it to her, she is Safek divorced. If the Tenai was verbal, he takes the Get from her and gives it without any Tenai or with a Kosher Tenai.

Beis Shmuel (5): Even a verbal Tenai of Chutz disqualifies if he said it when he gave the Get. The Get is Batel; he must give it again. A Tenai impossible to fulfill does not disqualify even if it was written before the Toref.

Beis Yosef (DH u'Mah she'Chosav v'Im): If he made a verbal Tenai 'Chutz mi'Ploni' or 'that you will never drink wine', he takes the Get gives it again.

Rebuttal (Beis Shmuel 6): He must take the Get back only regarding a Tenai of Chutz, which disqualifies to Kehunah (the Nesinah was not totally Batel). The Rambam (17) illustrates giving the Get again regarding a Tenai of Chutz mi'Ploni. The Shulchan Aruch (143:5,6) does not require taking back the Get when pardoning monetary Tena'im.'