Be careful what you term halaal and haraam
And do not say about what your tongues assert of untruth, "This is lawful and this is unlawful," to invent falsehood about Allah. Indeed, those who invent falsehood about Allah will not succeed.
Qur'ān 16:116
Imām al-Dārimi has narrated in his Musnad:
ما سمعت إبراهيم قط يقول حلال ولا حرام
al-'a'mash said: I never heard Ibrāhīm say this is halāl or this is harām
ولكن كان يقول : كانوا يكرهون وكانوا يستحبون
Rather, he used to say: They used to dislike (when they didn't deem something permissible) and they used to like (when they did deem it permissible)
وقال ابن وهب قال مالك : لم يكن من فتيا الناس أن يقولوا هذا حلال وهذا حرام
Imām Mālik said (paraphrase): It is not part of answering people in regards to legislative matters to say that this is halāl and this is harām
ولكن يقولوا إياكم كذا وكذا ، ولم أكن لأصنع هذا .
Rather, one should say beware of this and say that I would not do this
ومعنى هذا : أن التحليل والتحريم إنما هو لله - عز وجل - ،
The meaning of this is that making something permissible or making something harām is only for Allāh
وليس لأحد أن يقول أو يصرح بهذا في عين من الأعيان ، إلا أن يكون البارئ - تعالى - يخبر بذلك عنه .
And it is not for any person to say or explicitly claim that in regards to things unless Allāh has informed of the thing, in question, being harām or halāl
وما يؤدي إليه الاجتهاد في أنه حرام يقول : إني أكره كذا
As for the things which require Ijtihād to judge if they are harām, then one is to say I dislike such and such (if the Ijtihād leads the Mujtahid to believe it is harām).
وكذلك كان مالك يفعل اقتداء بمن تقدم من أهل الفتوى
And Imām Mālik used to do likewise following in the footsteps of those who preceded him in giving Religious verdicts.
Ibn Kathīr says (paraphrase):
ويدخل في هذا كل من ابتدع بدعة ليس [ له ] فيها مستند شرعي ، أو حلل شيئا مما حرم الله ، أو حرم شيئا مما أباح الله بمجرد رأيه وتشهيه
All those who innovate a bid'ah which has no support in Islamic legislation or make permissible what Allāh has made impermissble or make impermissble what Allāh has made permissible based only on conjecture are also a subject of the above Verse.
"...Indeed, those who invent falsehood about Allah will not succeed."
Imām al-Tabari says (paraphrase) regarding the above portion of the Ayah:
يقول: إن الذين يتخرّصون على الله الكذب ويختلقونه، لا يخلَّدون في الدنيا ، ولا يبقون فيها، إنما يتمتعون فيها قليلا
Allāh has said that the ones who fabricate lies about Allāh will not remain alive forever in this world. They only have a little enjoyment in this world.
Reference(s):
Tafsīr al-Tabari
Tafsīr Ibn Kathīr
Tafsīr al-Qurtubi