On the authority of Sufyan bin Abdullah (may Allah be pleased with him) who said:

“I said, ‘O Messenger of Allah, tell me something about Islam which I can ask of no one but you.’ He (peace be upon him) said, ‘Say “I believe in Allah” — and then be steadfast.'” [Muslim]

عَنْ أَبِي عَمْرٍو وَقِيلَ: أَبِي عَمْرَةَ سُفْيَانَ بْنِ عَبْدِ اللَّهِ رَضِيَ اللهُ عَنْهُ قَالَ:

“قُلْت: يَا رَسُولَ اللَّهِ! قُلْ لِي فِي الْإِسْلَامِ قَوْلًا لَا أَسْأَلُ عَنْهُ أَحَدًا غَيْرَك؛ قَالَ: قُلْ: آمَنْت بِاَللَّهِ ثُمَّ اسْتَقِمْ”

[رَوَاهُ مُسْلِمٌ].

On the authority of Abu Abdullah Jabir bin Abdullah al-Ansari (may Allah be pleased with him):

A man questioned the Messenger of Allah (peace be upon him) and said: “Do you think that if I perform the obligatory prayers, fast in Ramadan, treat as lawful that which is halal, and treat as forbidden that which is haram, and do not increase upon that [in voluntary good deeds], then I shall enter Paradise?” He (peace be upon him) replied, “Yes.” [Muslim]