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yā-ʾayyuhā lladhīna ʾāmanū ʾāminū bi-llāhi wa-rasūlihī wa-l-kitābi lladhī nazzala ʿalā rasūlihī wa-l-kitābi lladhī ʾanzala min qablu wa-man yakfur bi-llāhi wa-malāʾikatihī wa-kutubihī wa-rusulihī wa-l-yawmi l-ʾākhiri fa-qad ḍalla ḍalālan baʿīdan
O you who have faith! Have faith in Allah and His Apostle and the Book that He has sent down to His Apostle and the Book He had sent down earlier. Whoever disbelieves in Allah and His angels, His Books and His apostles and the Last Day, has certainly strayed into far error.
— Ali Quli Qarai
Surah An-Nisa', Verse 136
136. "O' you who have Faith believe in Allah and His Messenger and the Book which He has sent down unto His Messenger, and the Book (S) which He has sent down a foretime; and whoever disbelieves in Allah and His angels and His Messengers and the Last Day, has indeed gone astray into far error."
The meaning of the verse may be such: O' you who have faith! Go a step further; or, be firm in your faith forever. A believer should elevate himself to a higher degree of faith every day, since there are degrees in faith.
In this regard, Surah Muhammad, No.47, verse 17 says:
And, Surah Al-Fath No.48 verse 4 says:
However, disbelief, in some heavenly Books and some prophets is the same as disbelief in all.