Reading 1 - Job 8
Bildad (who speaks in Job 8; 18; 25) rests his philosophy on tradition (Job 8:8-10; 18:5-20). Like Eliphaz, Bildad has a far too rigid view of providence (Job 8:11-19; 18:5): that is, he believes that God will not "cast away" the perfect man (Job 8:20).
Reading 2 - Mic 4:8
"As for you, O watchtower of the flock, O stronghold of the Daughter of Zion, the former dominion will be restored to you; kingship will come to the Daughter of Jerusalem" (Mic 4:8).
The "watchtower of the flock" is "the tower of Edar (flock)"; this was a watchtower near Bethlehem (Gen 35:21), where shepherds watched over their flocks of sheep destined for sacrifice in the Temple.
This scene is fulfilled in Luke 2:8: "And there were shepherds living out in the fields nearby, keeping watch over their flocks at night."
"The former dominion will be restored to you; kingship will come to the Daughter of Jerusalem": "The former dominion" is the beginning, or the nucleus of the Kingdom, with Christ in the midst of Israel: Zec 8:23; Isa 60:3,5-9; 61:5,9; 62:1-3; Eze 37:26-28.
Literally, Jesus Christ was God's "first dominion": the first place on earth where the Father would reign supreme and unimpeded! The coming of this "first dominion" was first announced to the shepherds of Bethlehem, at the birth of Jesus (cp the imagery of childbirth in Mic 4:910), just as this verse prophesies.
The first place on earth where the dominion of "Christ the Lord" (Luke 2:11) was proclaimed was the hills near Bethlehem, the city of David. The angels sang of the birth of one in whom God would dwell in fullness, one who was the "kingdom of God" upon earth in its initial form. Christ would proclaim "glory to God" and "peace... toward men" (the true "peace" of sins forgiven, and reconciliation) (Luke 2:14). And he will finally bring that glory and peace in its consummate fullness when the true Kingdom comes at last to the "daughter of Zion".
Reading 3 - Heb 13:2
"Do not forget to entertain strangers, for by so doing some people have entertained angels without knowing it" (Heb 13:2).
Literally, show hospitality or love to strangers or foreigners. This is translated from the Greek "philoxenos" (1Ti 3:2), which occurs in the New Testament only here and Rom 12:13, although the related work ("hospitable") occurs also among the qualifications for elders listed in 1Ti 3:2 and Tit 1:8, and also 1Pe 4:9). Such hospitality is commanded by the Law of Moses (Deu 10:19) and in the New Testament (Rom 12:13; 1Pe 4:9; 1Ti 5:10). Those who care for the little ones care for Christ (Mat 25:38,40). Hospitality was highly esteemed in the ancient world and was certainly very important for Christians. Accommodation at inns was expensive, and in any case inns had a bad reputation. But as Christian preachers traveled around, believers gave them lodging and so facilitated their mission (see esp 3Jo 1:5-8). Without hospitality in Christian homes, the spread of the faith would have been much more difficult.
Some have entertained "angels" "without knowing it": Abraham (Gen 18:1-8) and Lot (Gen 19:1-3), but possibly also to Gideon (Jdg 6:11-22), and Manoah and the mother of Samson (Jdg 13:3-21). Angels also appeared to Hagar, Daniel, the shepherds, Peter, and many others. Compare the two at Emmaus (Luk 24:15-31). The writer is not advocating hospitality on the off chance that one might happen to receive an angel as guest but rather because God is pleased when believers are hospitable. Sometimes unexpectedly happy results follow acts of hospitality.
It is always possible God may manifest His care and protection in just such a way today -- the "without knowing it" reminds us that, even if this were to occur, we might never know when it did... when some "unnumbered comforts" were bestowed upon us!
Are there any reasons why we should think that an immortal angel could NOT appear to us today? None that I know of. Of course the verse does say "unawares"... so it sounds like, by the very nature of things, we wouldn't be able to prove it -- even if we were visited by angels of God. And we know, for that matter, that mortal men and women can be employed in the providence of God as His "messengers" (or angels). (The same thing was true in Bible times: think of the two spies who came to Rahab: the word in Jam 2:25 is "spies" in NIV, and "messengers" in KJV; it is in fact "aggelos" or angels. Similarly, Boaz entertained Ruth, and she proved to be a "messenger" from God, by which Boaz was richly blessed.)
But I wouldn't consider that examples of mortal "angels" being sent would necessarily rule out immortal "angels" being sent too. Any way, if nothing else (and even if we never know!), it's probably healthy to keep that thought in mind. It may make us kinder and more courteous to the next store clerk, or deliveryman, or homeless person, or internet correspondent we encounter.