Mudraj and its types

Mudraj[1] in reality is to mix the wording from the narrator with the wording of the ḥadīth narrated, without clarification. 

Mudraj is of two types:

1. Mudraj al-matn
2. Mudraj al-isnād

As for mudraj al-matn, this can occur in the beginning of the matn, the middle of the matn or the end of the matn, and this is most common. 

As for mudraj al-isnād this also takes different forms. 

We know when idrāj occurs when:

1. It is clarified in another narration.[2]
2. The rāwī clarifies the addition himself.
3. When other proficient scholars clarify there is idrāj.

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[1] Literally; inserted or included. 

[2] Such as the ḥadīth of ‘Abdullāh Ibn Mas’ūd when the Prophet ﷺ taught him tashahhud, the following words have been added by Ibn Mas’ūd, “إذا قلت هذا أو قضيت هذا فقد قضيت صلاتك إن شئت أن تقوم فقم وإن شئت أن تقعد فاقعد”. Imām al-Bayhaqī mentions that هذا حديث قد رواه جماعة عن أبي خيثمة زهير بن معاوية وأدرجوا آخر الحديث في أوله .