Why the silence?

But we should also note that the accounts of Abraham’s intercession (on behalf of Sodom and Abimelech) come before the Aqedah, at which time Abraham becomes strangely silent in the face of God’s command to sacrifice his son (he does not intercede for Isaac). As I suggested in my earlier discussion of Job (in chap 4), the reversal of Abraham from passionate speech (Gen. 18) to later silence (Gen. 22) may be addressed by Job’s own move in the other direction—from initial silence at the end of the prologue (implied in Job 2:13) to bold speech (starting in 3:1), and then again from his refusal to answer after God’s first speech (40:3–5) to his articulation of comfort after the second speech (42:6).—Abraham's Silence, 186–87