Shaykh Mufti Ashiq Illahi Bulandshahri mohajir Madani (Allah have mercy on him) said,

‘The issue of the rights of the fellow human beings (huqooq al-‘ibad) is of great enormity.  Commonly people are negligent about them. For them religiosity is limited to salah, (long) shirt and beard.

Shaykh Sufyan Thawri (Allah have mercy on him) used to say,

‘If an individual comes on the day of Judgment with seventy disobediences of Allah it is lighter sin than arriving there with a single obligation pending for a fellow human being.’

This is because Allah is self-sufficient (as-Samad) one can expect forgiveness from Him, whereas humans are needy. Therefore, it is essential to be vigilant about these rights. It is of immense importance that one clears these dues before death. It is a stupid idea to expect forgiveness from fellow humans on that day (of Judgment). They will be in need there in a a very tight situation. They will be looking for minute gains and all will try to claim their pending dues in full.

The situation in distribution of inheritance (merath) is sinful for almost all religious individuals, self-proclaimed pirs, scholars, and  lay public. The wealth (and property) of the deceased person is not distributed as per the Shariah rulings among the inheritors. The share of the widow and orphans is engulfed by others.’

Yadgar e Saliheen, Halaat e zindagi, page 104-5