Things God Can't Do?

Well, depending on how one views the question, there are many more than seven. Since I do not know what the focus of the particular sermon was, I will list just a few:

While God can do all things in accordance with his holy, divine nature which are consistent with his will (Gen. 18:14; 42:1-2; Jer. 32:17, 27; Matt. 19:26; Mark 10:27; Luke 1:37; 18:27; Rev. 19:6) he:

• (1) cannot die (Deut 32:39-40; Ps. 90:2; 102:27), nor can Jesus Christ die again (Rom. 6:9-10).
• (2) cannot stop being God (Mal. 3:6).
• (3) cannot lie (Heb. 6:18).
• (4) cannot be tempted with evil (Jas. 1:13).
• (5) cannot sin, as he cannot be tempted by evil (Jas 1:13).
• (6) cannot learn anything new, as he is all-knowing (Psa. 139:1-4; 1 John 3:20) and thus neither can he forget anything.
• (7) cannot be fooled (Num 32:23).
• (8) cannot be given a problem he cannot solve (Matt. 19:26). God can't make a rock so large that he could not move it (this is like asking a bachelor what his wife's name is), as this would not be consistent with his nature; God cannot and will not do illogical things (Isa. 55:8-9), so he also would not draw square circles. Even if he did (which he won't) what mere human finite mind could understand and define them?
• (9) cannot accept less than your whole heart (Deut. 6:5).
• (10) cannot change his ordained/decretive will (Dan. 4:35).
• (11) cannot change his Word (Psa. 119:89).
• (12) cannot lose one of his children (John 6:39).
• (13) cannot enjoy our sin (Isa. 59:2).
• (14) cannot keep from sending unrepentant people to hell, as he is holy and just and thus, according to his perfect nature, he must righteously judge people (Psa 77:13; Rom. 7:12; Matt. 25:41).
• (15) cannot (will not) allow his Church to be defeated (Matt. 16:18; Rom. 8:35-39; 1 Cor. 6:14).
• (16) cannot have human mood swings, as all God's emotions are rooted and flow from his divine holy nature and are always expressed sinlessly. See God's Impassibility and Feelings.

The Lord was with the men of Judah. They took possession of the hill country, but they were unable to drive the people from the plains, because they had iron chariots.

Many have read this verse quickly without any research and have come to the conclusion that God can do anything except defeat iron chariots. They say, "Yes, God can create the world from nothing, he can spilt the Red Sea, he can make the blind see, make the lame to walk, and he can walk on water, but he can't defeat iron chariots." Really?

If the Lord was with the men of Judah, why were iron chariots an issue? Had this not been promised? (Josh 17:16-18). Had they not had other difficult victories where God revealed his omnipotence? (Josh. 11:4-9). But notice, this was not Israel's only defeat. After this text in Judges 1, some of the shortcomings of the other tribes are also listed (Judges 1:21, 27; 29; 30; 31, 33). The Bible is clear that some failed to fully embrace the promises of God (Josh. 1:6-9) and sinned (Judg. 2:2-6; Num 33:52, 55; Jos. 23:13). Also remember that after the great defeat of Jericho came the humiliating defeat of Israel at Ai because of "sin in the camp" - Josh. 7.

Israel was not without sin. Additionally, the Bible reveals that God permitted these enemies to hold out in order to test the Israelites to see whether they would obey his commands (Judges 2:20-23; 3:1, 4). So, while all things are possible to God, he also does them in his own timing (Psa. 31:5; 75:2; Ecc. 3:17; Hab. 2:3), according to his own will (Eph. 1:11) and his express purposes (Rom. 8:28; Heb. 4:16), while allowing space to discipline his children as needed (Heb. 12:1-12). So, with regards to what God cannot do and iron chariots, it is rather something God "would not do" because of Israel's sin (Rom. 3:23) in order to justly test his children (cf. 2 Cor. 12:7-10).

While this list above is not complete, hopefully it includes the "things" you were seeking.