Midrasz do Lamentacje Jeremiasza 3:43

“You are covered with wrath and have pursued us; You have killed, did not have compassion. You have covered Yourself with a cloud so that no prayer can pass. You have rendered us filth and refuse in the midst of the peoples” (Lamentations 3:43–45).
“You are covered with wrath and have pursued us; You have killed, did not have compassion. You have covered Yourself with a cloud” – Rabbi Ḥelbo asked Rabbi Shmuel bar Naḥman, he said to him: ‘Because I heard about you that you are a master of aggada, what is this that is written: “You have covered Yourself with a cloud so that no prayer can pass”?’ He said: ‘Prayer is likened to a ritual bath, and repentance is likened to the sea. Just as the ritual bath is at times open and at times locked, so the gates of prayer are at times locked and at times open. However, the sea is always open. Rav Anan said: ‘The gates of prayer, too, are never locked. That is what is written: “Like the Lord our God whenever we call to Him” (Deuteronomy 4:7). Call is nothing other than prayer, as it is stated: “It will be that before they call I will answer”’ (Isaiah 65:24).
Rabbi Yosei bar Ḥalafta said: There are times for prayer, as so said David before the Holy One blessed be He: Master of the universe, when I pray before You, let my prayer be at a time of favor. That is what is written: “For me, let my prayer come to You, Lord, at a time of favor” (Psalms 69:14).
Rabbi Akiva was standing and being judged by Turnus Rufus, and Yehoshua HaGarsi was standing in prayer with him. A cloud descended and surrounded them. He said: It appears to me that this cloud descended and surrounded only so the prayer of my Master would not be heard. That is what is written: “You have covered Yourself with a cloud so that no prayer can pass.”
“You have rendered us filth and refuse [seḥi umaos] in the midst of the peoples” – despicable [masaya] and lowly [pesilaya].