Sheikh Nâsir al-Mâjid, professor at al-Imâm University in Riyadh
The scholars have agreed that it is lawful to read by any of the authentic styles of reading the Qur’ân (the qirâ’ât) - such as the seven readings - both in prayer and at other times.
Mixing between these different modes of recitation is a different matter. If such mixing occurs by mistake, then there is no disagreement that it is forgiven, according to Allah’s words: “Our Lord! Condemn us not if we forget or fall into error: our Lord Lay not on us a burden like that which thou didst lay on those before us, our Lord lay not on us a burden greater than we have strength to bear.” [Sûrah al-Baqarah: 268].
Also, our Prophet (peace be upon him) said: “Allah has forgiven my people for their mistakes and their forgetfulness and what they were coerced into doing.”
If, however, such mixing of styles is done intentionally, then we are faced with different opinions from the scholars regarding its permissibility. Ibn al-Jazirî in his book al-Nashr says something good regarding the rule of mixing more than one recitation style:
1. If such mixing spoils the Qur’anic style and affects or changes its meaning, then it is unlawful by the consensus of the scholars.
2. If mixing the readings does not spoil the Qur’anic style and does not change the meaning or spoil it then there are two situations. It is lawful to do so if the intent is merely to recite the Qur’ân, since all the different modes of recitation were sent by Allah and taught by the Prophet (peace be upon him) to ease the reading of the Qur’ân for people of different dialects. However, if the reader claims to be transmitting the style of a certain reciter, then mixing styles is unlawful, as this will deemed to be lying in transmitting the reading style and attributing a mode of reading to an Imam that he never performed.
And Allah knows best.
Source: Islam Today