On the authority of Ibn Abbas (may Allah be pleased with him), that the Messenger of Allah (peace and blessings of Allah be upon him) said:
Were people to be given everything that they claimed, men would claim the wealth and lives of people. But, the onus of proof is upon the claimant, and the taking of an oath is upon him who denies.
A hasan hadeeth narrated by al-Baihaqee and others in this form, and part of it is in the two Saheehs.
It is narrated on the authority of Amirul Mu'minin, Abu Hafs 'Umar bin al-Khattab (ra) who said:
I heard the Messenger of Allah (ﷺ) say: "Actions are (judged) by motives (niyyah), so each man will have what he intended.…
عَنْ عُمَرَ رَضِيَ اللهُ عَنْهُ أَيْضًا قَالَ: " بَيْنَمَا نَحْنُ جُلُوسٌ عِنْدَ رَسُولِ اللَّهِ صلى الله عليه و سلم ذَاتَ يَوْمٍ، إذْ طَلَعَ عَلَيْنَا رَجُلٌ شَدِيدُ بَيَاضِ الثِّيَابِ، شَدِيدُ سَوَادِ الشَّعْرِ، لَا يُرَى عَلَيْهِ أَثَرُ السَّفَرِ، وَلَا يَعْرِفُهُ مِنَّا أَحَدٌ. حَتَّى جَلَسَ إلَى النَّبِيِّ صلى الله عليه و سلم . فَأَسْنَدَ رُكْبَتَيْهِ إ…
Also on the authority of `Umar (ra) who said:
While we were one day sitting with the Messenger of Allah (ﷺ) there appeared before us a man dressed in extremely white clothes and with very black hair. No traces of journey…
On the authority of Abdullah, the son of Umar ibn al-Khattab (ra), who said:
I heard the Messenger of Allah (ﷺ) say, "Islam has been built on five : testifying that there is no deity worthy of worship except Allah and th…
On the authority of Abdullah ibn Masood (ra), who said:
The Messenger of Allah (ﷺ), and he is the truthful, the believed, narrated to us, “Verily the creation of each one of you is brought together in his mother’s womb f…
On the authority of the mother of the faithful, Aisha (ra), who said:
The Messenger of Allah (ﷺ) said, “He who innovates something in this matter of ours (i.e., Islam) that is not of it will have it rejected (by Allah).”…
On the authority of an-Nu’man ibn Basheer (ra), who said:
I heard the Messenger of Allah (ﷺ) say, “That which is lawful is clear and that which is unlawful is clear, and between the two of them are doubtful matters about…