Assalamu alaykum, Sufi scholars who justify celebrating milad, congregational dua after every prayer etc. as good Bidah justify that it is permissible to do bidah hasanah as there are evidences from ahadith. The folowing are the evidences they give. (1) Bukhari and Muslim relate from Abu Hurayra (Allah be well pleased with him) that at the dawn prayer the Prophet (Allah bless him and give him peace) said to Bilal, "Bilal, tell me which of your acts in Islam you are most hopeful about, for I have heard the footfall of your sandals in paradise", and he replied, "I have done nothing I am more hopeful about than the fact that I do not perform ablution at any time of the night or day without praying with that ablution whatever has been destined for me to pray." Ibn Hajar Asqalani says in Fath al-Bari that the hadith shows it is permissible to use personal reasoning (ijtihad) in choosing times for acts of worship, for Bilal reached the conclusions he mentioned by his own inference, and the Prophet (Allah bless him and give him peace) confirmed him therein. Similar to this is the hadith in Bukhari about Khubayb (who asked to pray two rakas before being executed by idolaters in Mecca) who was the first to establish the sunna of two rak'as for those who are steadfast in going to their death. These hadiths are explicit evidence that Bilal and Khubayb used their own personal reasoning (ijtihad) in choosing the times of acts of worship, without any previous command or precedent from the Prophet (Allah bless him and give him peace) other than the general demand to perform the prayer. (2) Bukhari and Muslim relate that Rifa'a ibn Rafi said, "When we were praying behind the Prophet (Allah bless him and give him peace) and he raised his head from bowing and said , "Allah hears whoever praises Him", a man behind him said, "Our Lord, Yours is the praise, abundantly, wholesomely, and blessedly therein." The companion said the statemeeven without Prophet's prior approval

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

We have already clarified the definition of Bid'ah (innovation in religion) and the meaning of a Bid'ah Hasanah (good innovation) in Fataawa 2741, 17613 and 91407.

However, the Ahaadeeth that you have mentioned are not evidence for the Sufis for their innovation. Bilaal had performed a permissible act of worship which is the prayer, and when he performed it after ablution and the Prophet approved this act, we knew that this act was permissible after ablution, whereas the Sufis do an impermissible act of worship which is celebrating the Mawlid (birthday of the Prophet ).

On the other hand, Ibn Hajar said that it is permissible to make Ijtihaad (personal diligence) in allocating a time for an act of worship but he did not say that it is permissible to make Ijtihaad in innovating a new act of worship, and the story of Khabbaab proves this.

As regards the mention of Allaah that the Companion said when he raised his head from Ruku’, when the Prophet approved this act, we knew that this act was permissible, and it was at the time of legislation [revelation being sent down] when a Companion may do an act or say a statement and it will be approved from him (i.e. by the Prophet ). Having said that, a Companion may do an act or say a statement and it will not be approved from him as what happened when Al-Baraa’ ibn ‘Aaazib was taught by the Prophet to say the supplication for going to sleep which includes “…and your Prophet, whom You have sent,” and Al-Baraa’ changed the wording saying “…and your Messenger, whom You have sent.” So, the Prophet did not approve of this wording and told him  “'No, and your Prophet whom You have sent'.” [Al-Bukhari]

Therefore, the Sufis comparing their innovation to what Bilaal and Khabbaab did is an inappropriate analogy.

Allaah Knows best.