Arabic text
عَنْ أَبِي عَمْرٍو- وَقِيلَ: أَبِي عَمْرَةَ-، سُفْيَانَ بْنِ عَبْدِ اللَّهِ رَضِيَ اللَّهُ عَنْهُ قَالَ: قُلْتُ: يَا رَسُولَ اللهِ، قُلْ لِي فِي الْإِسْلَامِ قَوْلًا لَا أَسْأَلُ عَنْهُ أَحَدًا غَيْرَكَ، قَالَ: «قُلْ: آمَنْتُ بِاللهِ، ثُمَّ اسْتَقِمْ».
Translation
Abu ‘Amr—and it was said: Abu ‘Amrah—Sufyān ibn ‘Abdullah (may Allah be pleased with him) reported: I said: O Messenger of Allah, tell me something about Islam regarding which I can ask none but you. He (may Allah's peace and blessings be upon him) said: "Say: I believe in Allah, then remain steadfast."
Explanation
Sufyān ibn ‘Abdullah, the Prophet's Companion, (may Allah be pleased with him) asked the Prophet (may Allah's peace and blessings be upon him) to teach him a comprehensive statement that comprises all the meanings of Islam so as to adhere to it and ask no one else about it. The Prophet (may Allah's peace and blessings be upon him) said to him: Say: I believe in Allah as the only deity, and I believe that He is my Lord, my God, my Creator, and the only God Who is truly worthy of my worship, with no partner. Then, submit to Allah and obey Him by performing what He has enjoined, avoiding what He has forbidden, and remaining steadfast on that.
Source: HadeethEnc.com