From The Holy Quran with English Translation and Commentary by Hazrat Alhaj Mirza Bashir-ud-Din Mahmud Ahmad (introduction to Surah Fatiha)

Muslims are bidden always to begin the reading of the Holy Book with a short prayer, soliciting God’s protection against Satan. God says:

And when thou recitest the Qur’an, seek refuge with ALLAH from Satan, the rejected. (16:99)

Now, refuge or protection implies:

1. That no evil should befall us;
2. That no good should escape us; and
3. That after we have attained goodness, we may not relapse into evil.

Thus, by seeking the protection of God while reciting the Quran we pray, firstly, that we may not miss any teaching of the Quran through weakness or negligence or in consequence of our sins, or under the influence of evil company; secondly, that we may not fail to understand rightly any teaching of the Quran; thirdly, that, having understood, we may not relapse into ignorance again. The prescribed words for the prayer are, ‘I seek refuge with Allah from Satan, the rejected,’ which must precede every recitation of the Quran.