Rambam Laws of Forbidden Relations Chapter 13
There are three ways in which someone enters the covenant: by circumcision, by immersion, and by a Temple offering.
Circumcision as it was in Egypt, as it says, "Every uncircumcised person shall not eat of it (the Passover offering)." Moses our teacher circumcised them and everyone spurned the covenant in Egypt with the exception of the Tribe of Levi. On this it says, "Your covenant was withheld."
Immersion was in the desert before receiving the Torah, as is said, "Sanctify yourselves today and tomorrow; wash your clothes." The offering, as is said, "Send the young ones of Israel to bring elevation offerings" - and everyone in Israel brought them.
Throughout the generations, any non-Jew who wants to enter the covenant and come in under the 'wings of the Presence of God' accepts upon him or herself the yoke of Torah - he needs circumcision, immersion and a Temple offering. If female, she needs only immersion and an offering, as is said "As for you, so for the foreigner." That's to say, just as you (entered via) circumcision, immersion and an offering, so too the foreigner (shall enter via) circumcision, immersion and an offering.
For this reason, our Sages said: "Converts are as difficult for the Jewish people to bear as a leprous blemish." For most converts convert for an ulterior motive and [later] cause Jews to stray. It is difficult to separate from them once they have converted. Look at what happened in the desert at the worship of the Golden Calf and Kivrot HaTa'avah. Similarly, most of [the complaints in the instances when] our people tried God were instigated by the mixed multitude.
Rabbi Tzvi Hirsch Kalischer (1795-1874)
You should not refrain from circumcising a boy whose father is Jewish as we are commanded to grant him the opportunity to be circumcised immmediately at the directive of his father. Thus, when he grows up, he will quickly be able to perform the willl of his father by ritually immersing himself according to the Jewish law of conversion.
Rabbi Eliezer Melamed (Israel, 21st Century)
The question is as follows: In order to avoid intermarriage can a rabbi convert a non-Jew to observe a traditional Jewish lifestyle without a commitment to complete observance of the mitzvah?
In recent years, I have come to the conclusion that one may convert a non-Jew who will observe a traditional Jewish life in order to avoid intermarriage.
Letter Signed by 40 Israeli Rabbis, May 2022
A series of articles have come to our attention where a rabbi has permitted conversion of non-Jews who will not aceept to live bound by all the mitzvot but only as a traditional Jew. This view is very dangerous since it will allow non-Jews to enter the community even though their conversion is inadequate. No conversion can be performed without a commitment to live a life of complete observance of mitzvot.