It is befitting for one reciting the Qur’an, that he/she approaches Allah’s Book with the best of manners, humility and respect. He/she should be sitting up and not leaning nor sitting in any disrespectful or arrogant way. The best recitation of all is done in Salah while standing, and the best of that is in the mosque. However, it is not Haram to recite the Qur’an while leaning or sleeping if there is a reasonable cause for doing so.
The Prophet (peace and blessings be upon him) is reported to have recited the Qur’an in all postures, even when he was resting on `A’ishah’s lap, when she was menstruating.
Describing the true believers, Allah Almighty says in the Qur’an: ” Such as remember Allah, standing, sitting, and reclining, and consider the creation of the heavens and the earth, (and say): Our Lord! Thou createdst not this in vain. Glory be to Thee! Preserve us from the doom of Fire.” (Al `Imran: 191)
Sheikh `Abdul-Majeed Subh, a prominent azharite scholar, says: “It is strongly recommended to recite Ayat Al-Kursi (verse no. 255 in surat Al-Baqarah) and the last two verses of surat Al-Baqarah when one lies down to sleep. Therefore, there is nothing wrong in reciting the Qur’an while lying down. Allah Almighty says: “When ye have performed the act of worship, remember Allah, standing, sitting and reclining. And when ye are in safety, observe proper worship. Worship at fixed times hath been enjoined on the believers.” (An-Nisa’: 103)”