Ma'ṣūm vs. Maĥfūż: what is the practical difference?
Scholars have stated that Prophets are ma'sūm (i.e. infallible, protected from committing sins) and that the Companions of the Prophet Muhammad ﷺ are maĥfūz (literally; "safeguarded/protected"). A question does arise: what is the practical difference between two? No conclusive research seems to have been done on this issue.
We know through many reports that the Companions did commit sins, by their own admission. So how are they then maĥfūż?
A while back I read an interesting taĥqīq by a late Subcontinent scholar by the name of Ghulam Rasool Saeedi. One of the scholars in my locality wrote a PhD thesis on his tafarrudāt (anomalous opinions) and this issue was addressed in the section of creed.
Shaykh Ghulam Rasool writes that 'isma (infallibility) entails that Prophets, despite being physically able to commit sins, don't do so due to fear of the Divine [khashyat-e-ilāhī] being prevalent within their hearts. Hence their not committing sins is a perfection, whereas if it weren't physically possible for them to do so, it wouldn't make sense to oblige them to abstain from committing sins. At times Prophets had ijtihādi slip-ups [khaṭā'en]; however, through revelation they would be made aware of them and immediately rectify them. However, our Prophet Muhammad ﷺ never had ijtihādi slip-ups according to the researching scholars [muhaqqiqīn].
As for the Sahaba's being maĥfūż, it entails that, per human nature, they commit sins at times; however, they are always enabled [tawfīq de dī jātī hai] to repent from their sins prior to passing away.
So Sahaba's being maĥfūż means that they don't pass away prior to being enabled to repent from their sin. Take for example the Sahaba that wrongly accused our Mother Aisha (may Allah be pleased with her), all of them repented prior to passing away. Likewise, all the wives of the Prophet ﷺ are maĥfūż too; at times they had slip-ups too, but they never remained upon them and immediately repented from them.