Week Forty is the second week of Tammuz, and Haazinu’s verse refers to G-d making an oath, raising His hands to heaven. (Interestingly, in Book 1, the wolf’s song during this week also makes reference to an oath). An oath adds additional weight and power, as well as determination and foundation (“yesod”).
The Haftorah verse for this week speaks again of G-d girding King David with strength for battle. King David’s previous verses (since the week of Lag Ba’omer) had all been about being fortified and being victorious in battle. Perhaps the repetition is to indicate that in conquest it is often not sufficient to be victorious once. One has to show a certain amount of yesod, being able to encounter the same situation over and over again, and remain victorious without budging.
The quality for this week is "bears the burden with one's friend" (noseh b’ol im chaveroh). The quality is not "bears the friend’s burden," but rather that both should share the burden together. This burden, or yoke, could even be referring to the yoke of Torah, which nevertheless needs acquiring day in and day out – an ongoing battle that takes place during one’s entire life.
This week’s prophet is Neriah. Not much is known about Neriah, other than that he was the father of Baruch, the prophet of the previous week. Neriyah was related to and a contemporary of other prophets mentioned this month (Baruch, Machseyah, Serayah, as well as Huldah), who had the burden of giving the news of the upcoming destruction. The name Neryah means the "candle of G-d," and ultimately that is what we all are at our essence, One soul.