All Major Innovations and Deviations Begin Small and Insignificant
Beware of small innovations because they grow until they become large.[1]

This is the case with every innovation introduced in this Ummah. It began as something small, bearing resemblance to the truth which is why those who entered it were mislead and then were unable to leave it. So it grew and became the religion which they followed and thus deviated from the Straight Path and left Islaam.[2]

[1] A striking example of how small innovations lead a  person into committing major innovations is found in the narration reported by ad-Daarimee in his Sunan (1/79)

al-Hakam bin al-Mubaarak informed us that Amr ibn Yahyaa said my father related from his father who said:

“We used to sit by the door of ‘Abdullah ibn Mas’ood before the Salaatul Ghadaat (morning prayer), so that when he came out we would walk with him to the masjid. (One day) Aboo Moosaa al-Ash’aree came to us and said, “Has Aboo ‘Abdur-Rahmaan come out yet?” We replied, “No.” Therefore, he sat down with us until he came out. When he came out, we all stood along with him,

so Abu Moosaa said to him, “O Aboo ‘Abdur-Rahmaan I have just seen something in the masjid which I deemed to be evil, but all praise is for Allaah, I did not see anything except good!”

He inquired, “Then what is it?”

(Aboo Moosaa) replied, “If you live you will see it. I saw in the masjid people sitting in circles awaiting the Prayer. In each circle they had pebbles in their hands and a man would say ‘repeat Allaahu Akbar a hundred times.’ So they would repeat it a hundred times. Then he would say, ‘say Laa ilaaha illallaah a hundred times.’ So they would say it a hundred times. Then he would say, ‘say Subhaanallaah a hundred times.’ So they would say it a hundred times.”

(Ibn Mas’ood) asked, “What did you say to them?”

(Aboo Moosaa) said, “I did not say anything to them. Instead I waited to hear you view or what you declared.”

(Ibn Mas’ood) replied, “Would that you had ordered them to count up the evil deeds they acquired and assured them that their good deeds would not be lost!”

Then we went along with him (Ibn Mas’ood) until he came to one of these circles and stood and said,

“What is this which I see you doing?”

They replied, “O Aboo ‘Abdur-Rahmaan! These are pebbles upon which we are counting takbeer, tahleel and tasbeeh.”

He said, “(You should) count your evil deeds and I will assure you that none of your good deeds will be lost. Woe to you, O Ummah of Muhammad (sallallaahu alayhi wasallam)! How quickly you are rushing to your destruction! These are the Companions of your Prophet (sallallaahu alayhi wasallam) and who are widespread (and numerous). There are his clothes which have not yet decayed and his eating utensils which are unbroken. By Him in Whose Hand is my soul! Either you are upon a deen better guided than the Deen of Muhammad (sallallaahu alayhi wasallam) or that you are opening the door of misguidance (from this bid’ah).

They said, “O Aboo Abdur-Rahmaan! By Allaah, we only intended good.”

He said, “How many there are who intend good but do not achieve it. Indeed Allaah’s Messenger said to us ‘A people will recite the Qur’aan but it will not pass beyond their throats.’ By Allaah! I do not know, perhaps most of them are from you.” Then he left them.

Umar ibn Salamah (the sub-narrator) said: “We saw most of those people fighting against us on the day of Nahrawaan, along with the Khawaarij.”

From the introduction of ad-Daarimee, volume one, page 73 with an authentic chain.

[2] The scholars differentiate between those innovations which take  a person outside the fold of Islaam (al-Bid’atul-Mukaffirah) and those which do not. So this is not to be understood unrestrictedly.

Reference for above:
“Explanation of the Creed” of Al-Barbahaaree (translated By Abu Talhah Dawud Burbank) on page 5

Internet Source: Group Dhikr

Related Links:

A Scholarly Research by Shaykh Albaani That Prayer Beads are a Bida’ [PDF] Taken from ‘Silsilah Ahadeeth ad-Daeefah’1/83
A summary of the research by the Shaykh, Allamaa’ Muhammad Nasiruddeen al-Albaani

[online class] Sharhu Sunnah by Imam al Barbaharee – by Mustafa George (Hafidahullah)