Is it considered sound conduct to relinquish rights for fear of falling into the unlawful, such as foregoing the purchase of items due to suspicion about the permissibility of their source?

Lenience in worship is not characteristic of believers. The commands of Allah and His Messenger must be applied to the best of one's ability, for Allah Almighty says: "And let those who oppose His command beware, lest fitnah strike them or there come upon them a painful punishment." And the Prophet, peace and blessings be upon him, said: "What I have forbidden for you, avoid; and what I have commanded you to do, do of it as much as you are able." Avoiding the forbidden is obligatory, but exaggeration in it (extremism/being overly scrupulous) is blameworthy, as the Prophet, peace and blessings be upon him, said: "The extremists are ruined." Circumventing to throw away fruits and the like, and refraining from buying things for fear of their source, falls under extremism and is not piety. An orphan, in Islamic law, is one who has lost his father. Avoiding consuming the property of others is obligatory, even if the owner is not an orphan.