I heard that Qasidah Burdah is Bida'h is that true or not?

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions. The poet who composed this poem, by name of "al-Burdah" (the garment), which was intended to praise the Prophet (may Allah's peace and blessing be upon him), fell in the disapproved excessive eulogy. The Prophet (Sallallahu Alaihi wa Sallam) warned against such excessive laudation. He said: Never extol me as the Christians did extol the Son of Mary (Jesus Christ, peace be upon him), for I am no more than a slave of Allah, so say nothing more than 'His slave and messenger . [Reported by al-Bukhari ] Such disapproved extolment can be seen through the poet's saying: "O ye, Noblest of the creatures! I have none except thee To whom I may resort when serious afflictions befall me" And: "Thy knowledge has encompassed the Preserved Tablet and the Pen" These exaggerated sayings involve blatant ignorance and constitute a flagrant contradiction to the clear texts which confirm that the knowledge of the Unseen is limited to Allah Almighty alone: {And with Him are the keys of the Ghaib (all that is hidden), none knows them but He…}[6:59] and He Says: {….If I had the knowledge of the Ghaib (unseen), I should have secured for myself an abundance of wealth, and no evil should have touched me. I am but a warner, and a bringer of glad tidings unto people who believe.}[7:188]. None except Allah The Almighty can be addressed in such a way. Among His Creation are this life (mundane) and the Hereafter, and within His infinite Knowledge are the Preserved Tablet and the Pen. The Prophet (Sallallahu Alaihi wa Sallam) never claimed to know of what Hidden (the Unseen) except what Allah let him know. The Noble Qur'an and the Sunnah (the Prophet's Tradition) do not contain any clue that Allah made His Prophet to know anything of what is in the Preserved Tablet or what His Pen (of predestination) has decreed. Far from that, the Qur'an and the Sunnah stressed the fact that the Prophet did not know many of the issues relating to his time's affairs. An example for that is the verse: {…And among the bedouins round about you, some are hypocrites, and so are some among the people of Al-Madinah, they exaggerate and persist in hypocrisy, you (O Muhammad SAW) know them not, We know them….}[9:101]. As for the pieces of evidence from the Prophet's Noble Biography and Sunnah, they are innumerable. Among the examples proving this fact are: what happened during the Battle of Uhud, his eating from the poisoned ewe, the death of one of his companions because of that ewe, what happened concerning the Ifk event (the false accusation fabricated against his chaste wife Ayisha (Radiya Allahu Anha), his intention to attack the tribe of Bani al-Mustaliq, and the revelation of the verse: {O you who believe! If a rebellious evil person comes to you with a news, verify it….}[49:6] and so on. All these matters are evidence that the Prophet (Sallallahu Alaihi wa Sallam) did not know anything related to the Preserved Tablet or the Hidden knowledge (the Unseen) except what Allah made him to know through revelation. From that we are to know that the poet's saying: "O ye who had the knowledge of the Tablet and touched the Pen" is over exaggeration and mere falsification. Such allegation involves the great sin of approaching the matters of religion without knowledge. One has to beware of such matters as excessive lauding and over extolment, and abide by moderation and reasonability. May Allah guide us all to do so. For further details on the criticism of this poem, you might refer to a book entitled "Criticism of Al-Burdah, with Answers and Corrections". Allah knows best.