Abbas - Tanwîr al-Miqbâs min Tafsîr Ibn ‘Abbâs
(Lo! those who disbelieve in Allah and His messengers) meaning Ka'b and his followers, (and seek to make distinction between Allah and His messengers) with regard to prophethood and surrender to Allah, (and say: We believe in some) Scriptures and messengers (and disbelieve in others) in other scriptures and messengers, (and seek to choose a way) a religion (in between) between disbelief and faith;
Those who disbelieve in God and His messengers and seek to divide between God and His messengers, by believing in Him but not in them, and say, ‘We believe in some, of the messengers, and disbelieve in some’, of the others, and seek to adopt a way, a path, to follow, between them, [between] unbelief and belief.
Those who disbelieve, [those] who veil themselves from the Truth and from religion, and from the union and from differentiation, and seek to divide between God and His messengers, by veiling themselves from religion but not the Truth and from differentiation but not the union, and so deny the messengers estimating that unity is incompatible with multiplicity and that union is inconsistent with differentiation: that is how they end up believing in some things and disbelieving in others: [and say, 'We believe in some, and disbelieve in some'] and seek to adopt, a way between total faith, in union and differentiation, and total disbelief.
Believing in Some Prophets and Rejecting Others is Pure Kufr
Allah threatens those who disbelieve in Him and in His Messengers, such as the Jews and Christians, who differentiate between Allah and His Messengers regarding faith. They believe in some Prophets and reject others, following their desires, lusts and the practices of their forefathers. They do not follow any proof for such distinction, because there is no such proof. Rather, they follow their lusts and prejudices. The Jews, may Allah curse them, believe in the Prophets, except `Isa and Muhammad, peace be upon them. The Christians believe in the Prophets but reject their Final and Seal, and the most honored among the prophets, Muhammad, peace be upon him. In addition, the Samirah (Samaritans) do not believe in any Prophet after Yuwsha` (Joshua), the successor of Musa bin `Imran. The Majus (Zoroastrians) are said to believe only in a Prophet called Zoroaster, although they do not believe in the law he brought them casting it behind them, and Allah knows best. Therefore, whoever rejects only one of Allah's Prophets, he will have disbelieved in all of them, because it is required from mankind to believe in every prophet whom Allah sent to the people of the earth. And whoever rejects one Prophet, out of envy, bias and personal whim, he only demonstrates that his faith in other Prophets is not valid, but an act of following desire and whim. This is why Allah said,
إِنَّ الَّذِينَ يَكْفُرُونَ بِاللَّهِ وَرُسُلِهِ
(Verily, those who disbelieve in Allah and His Messengers...) Thus, Allah describes these people as disbelievers in Allah and His Messengers;
(saying, "We believe in some but reject others,'' and wish to adopt a way in between.) Allah then describes them;
أُوْلَـئِكَ هُمُ الْكَـفِرُونَ حَقّاً
(They are in truth disbelievers.) meaning, their disbelief in the Prophet they claim to believe in is clear. This is because their claimed faith in a certain Messenger is not true, for had they truly believed in him, they would have believed in other Messengers, especially if the other Messenger has a stronger proof for his truthfulness. Or at least, they would have strived hard to acquire knowledge of the truth of the other Messenger. Allah said,
وَأَعْتَدْنَا لِلْكَـفِرِينَ عَذَاباً مُّهِيناً
(And We have prepared for the disbelievers a humiliating torment.) This is just punishment for belittling the Prophets whom they disbelieved in, by ignoring what the Prophet brought to them from Allah, and because they are interested in the insignificant possessions of this world. Or, their behavior could be the result of their disbelief in the Prophet after they were aware of his truth, just as the Jewish rabbis did during the time of Muhammad, the Messenger of Allah. The Jews envied the Messenger because of the great prophethood that Allah gave him, and as a consequence, they denied the Messenger, defied him, became his enemies and fought against him. Allah sent humiliation upon them in this life, that shall be followed by disgrace in the Hereafter,
(And those who believe in Allah and His Messengers and make no distinction between any of them,) This refers to the Ummah of Muhammad who believe in every Book that Allah has revealed and in every Prophet whom Allah has sent. Allah said,
(The Messenger believes in what has been revealed to him from his Lord, and (so do) the believers. All of them believe in Allah.) (2:285). Allah then states that He has prepared great rewards for them, tremendous favor and a handsome bounty,
أُوْلَـئِكَ سَوْفَ يُؤْتِيهِمْ أُجُورَهُمْ
(We shall give them their rewards;) because of their faith in Allah and His Messengers,
وَكَانَ اللَّهُ غَفُوراً رَّحِيماً
(and Allah is Ever Forgiving, Most Merciful.) for their sin, if they have any.
Maududi - Sayyid Abul Ala Maududi - Tafhim al-Qur'an
That is, there is absolutely no doubt that all those people are equally disbelievers, who deny Allah all His Messengers: who acknowledge Allah but deny His Messengers: who accept some of the Messengers and reject others: each and everyone of such people is a confirmed disbeliever.
Full assurance has been given to those who acknowledge Allah as their sole Sovereign and Deity, and submit to and follow all His Messengers, that they deserve to be rewarded according to the quality of their good deeds. In contrast to them, there is ignominious punishment for those who do not acknowledge Allah as the sole Sovereign and Sustainer, or for those who adopted the rebellious way by accepting some of His representatives and rejecting others. Allah does not accept any of the apparently good deeds of such people because it has no legal status in His sight.
As Allah is Forgiving and Compassionate, He will be very lenient in judging the deeds of those who believe in Him and His Messengers and will not be hard on them.
Those who disbelieve in God and His messengers and seek to divide between God and His messengers and say “We believe in some and disbelieve in some” and seek to adopt a way between them. Those are the disbelievers truly; and We have prepared for the disbelievers a humiliating chastisement. [God] relates that they have added the blameworthy actions enumerated here to the shamefulness of their disbelief. He explains that He has doubled their chastisement as requital for their sin so that you will know that He is ever on the watch [89:14] over those who act in corrupt and harmful ways.