Canto 5&6

Canto 5
1. "Beware how you come in and whom you trust" (pg. 47). This tells us that, while Virgil is Dante's guide, he will not be the one who makes all the decisions of what they do while they pass through Hell. Dante will still have to think and make decisions for himself. He will have to choose which souls would be useful in helping them out. There is a tone of warning in Minos's statement that if Dante doesn't choose well he will get stuck in Hell.
2. "Swooning as in death, I fell like a dying body" (pg. 53). As soon as we see Dante feeling pity for the lovers and the sins that brought them to Hell, his soul faints from the exhaustion of pushing against the call of death. His emotional connection with the lovers is preyed upon by the evils of Hell and he finds it so hard to with stand the pull of sin that his physical body gives out. The fact that Virgil didn't do anything to warn Dante of the dangers of speaking with the souls suggests that Dante must learn on his own how to not get too close to them.
Canto 6
1. "Treading upon their emptinesses, which seemed like real bodies" (pg. 59). This suggests that the souls have become empty of the things that a soul should have, like love, joy and happiness. Instead, they have been beaten down by the rain and the noise of Cerberus' barking. The sin of Gluttony (which would make a person full), leads to this emptiness. These souls are condemned to this in death because of their greed for more in life.
2. "and the hostile Power comes" (pg. 61) Most religious people don't think of God's power as being hostile, but this line brings to light the feelings of those who don't believe in God, or don't follow his way. To them, His judgements would seem harsh because of his wrath for those who disobey Him.