Many of these tribulation saints no doubt suffered physical deprivation during their time of persecution (Mtt. Mat. 25:31-46; Rev. Rev. 13:17+), not to mention the harsh conditions upon the earth during this time: Rev. 6:5-6+), their deprivation of water of the third trumpet (Rev. Rev. 8:10-11+), and the heat of the sun of the fourth bowl (Rev. Rev. 16:8-9+). In other words, these martyrs will come from all phases of the tribulation judgments depicted in Revelation.1 God also satisfies the spiritual hunger of the longing soul (Ps. Ps. 107:9; John John 4:14; John John 6:35). These are among the blessed ones who hunger and thirst for righteousness and shall be filled (Mtt. Mat. 5:6).
nor any heat
In their wilderness wanderings, Israel was sheltered from the heat by the cloud which covered the camp during the day (Num. Num. 10:34 cf. Isa. Isa. 4:4-6). Isaiah was also given revelation concerning this truth: in the day of salvation, the Father gave the Son as a covenant to the people. He would go forth to the sheep who were in darkness so that they would be fed. They would no longer hunger or thirst, nor would they suffer from the heat or sun. And He would lead them by the springs of water (Isa. Isa. 49:8-10). Those who reject God will feel intense heat before His judgments are complete (Rev. Rev. 16:8+).
1 Monty S. Mills, Revelations: An Exegetical Study of the Revelation to John (Dallas, TX: 3E Ministries, 1987), Rev. 7:16.