All perfect praise be to Allah the Lord of the Worlds. May His blessings and peace be upon our Prophet Mohammad and upon all his family and companions.
It was narrated from 'Abdullah bin Yasar, from Qutailah, a woman from Juhainah, that a Jew came to the Prophet and said:
"You are setting up rivals (to Allah) and associating others (with Him). You say: 'Whatever Allah wills and you will,' and you say: 'By the Ka'bah.'" So the Prophet commanded them, if they wanted to swear an oath, to say: "By the Lord of the Ka'bah;" and to say: "Whatever Allah wills, then what you will." { Sunan an-Nasa'i 3773}.
The apparent meaning of this Hadith indicates that the Prophet (Peace be upon him) approved of his companions` associating partners in worship with Allah until the Jew came and brought that to his attention. This can be clarified in many respects:
First: This is a da'if hadith (a hadith which does not fulfil the conditions of the sahih or hassan hadith). Moreover, the chain of transmitters (Isnad) is wrong and this mistake was made by M`abad Bin Khalid. The correct Isnad is that it was narrated from Mansour, from Abdullah Bin Yasar, from Huthaifa Bin Al-Yaman and not from Qutailah. This view was supported by Al-Bukhari who said: "The Isnad from Mansour is the most correct."{Al-Elall Al-Kubra No.(457)}. The Hadith in the above question means that it was narrated from Abdullah Bin Yasar, from Huthaifa Bin Al-Yaman although the latter haven`t heard it from the former; consequently, this Hadith is da`if and interrupted (There is a missing transmitter between these two). For more details, kindly check {Tarikh Ibn Mo`ein Rewayat Ad-Darimi, P.160} by Ad-Darimi.
Second: Supposing that the narration from Huthaifa Bin Al-Yaman is authentic, there is no mention of the Jew. It states that the Prophet (Peace be upon him) said to the companions to say: "Whatever Allah wills, then what you will."{Related by Ahmad in his Musnad (38/300). Thus, the correct narration has no mention of what the Jew had said.
Third: Supposing that what Ma`bad Bin Khalid cited is true, it doesn`t mean that the Prophet (Peace be upon him) approved of what the Jew said (You associate others in worship with Allah). Rather, it means that the phrases (Whatever Allah wills and you will) and ('By the Ka'bah) were used at the advent of Islam and, later, they were abrogated by the Prophetic Sunnah when the Prophet (Peace be upon him) forbade these phrases. Moreover, these phrases aren`t an act of Shirk (Ascribing partners in worship to Allah) that drives a person out of the fold of Islam. Rather, they must be avoided out of respect for Allah.
Fourth: The Prophet (Peace be upon him) didn`t hear any of the companions using such phrases. Rather, the Jew heard that some of companions said so and told the Prophet (Peace be upon him), so he (Peace be upon him) forbade them. Here, this is considered a minor Shirk, which doesn`t expell a person out of the fold of Islam. And Allah the Almighty knows best.