Before we look at each of these it is important to note that tithes, pledges, and offerings are all related to the nation of Israel. They are NOT referred to at all in relation to the church of God, so believers today are not responsible to give them. So, the answer to your second question is there is NO PUNISHMENT for not giving the right tithes since believers in Christ today are not commanded to give them. Now let us consider briefly the difference between these three.

TITHES…the word simply means “a TENTH.” The first mention of this word is in Genesis 14:20 where we are told that Abraham “gave him (Melchizedek) a TITHE of all.” It is instructive to see that with Melchizedek we have the FIRST MENTION OF A PRIEST (in verse 18) and the FIRST MENTION OF A TITHE (in verse 20). Are they related? I believe they are, for once God instituted the Levitical Priesthood under the Law of Moses, God commanded the children of Israel to “support the Levitical priests with tithes,” for they had no inheritance in the land and their full-time job was ministering as priests in God’s sanctuary (see Numbers chapter 18). So, even though Melchizedek was not a priest under the Law of Moses (for the Law had not yet been given), Abraham acknowledged him as a priest, and he gave him “10% of all that he had” in order to support his priestly work. Believers in the church of God are never told to “support a special order of priests” today with tithes. The fact is “all believers today are priests” (see 1st Peter 2:4-10) and we don’t serve God in an earthly sanctuary and we don’t need the financial support of other believers (though some are called to go out in full-time service for the Lord and they are supported by believers who voluntarily give them gifts (1st Corinthians 9:1-14; 2nd Corinthians 9:7).

PLEDGES…this word is only found in the Old Testament. A “pledge” was something given to someone as security for the fulfillment of a contract or the payment of a debt. We read of this in Exodus 22:25-26, “If you lend money to any of My people who are poor among you, you shall not be like a moneylender to him; you shall not charge interest. If you ever take your neighbor’s GARMENT AS A PLEDGE, you shall return it to him before the sun goes down.” So, a pledge is given to someone who you have borrowed something from as a guarantee to pay them back, but a tithe was given to the priests in Israel. We do not find this word in the New Testament so believers in Christ are not commanded to give pledges.

OFFERINGS…This word is found mostly in the Old Testament, though it is also found in Mark 12:33; Luke 21:4; Acts 24:17 and Hebrews 10: 6 & 8 where it relates to the nation of Israel and not to the church. The word refers primarily to “sacrifices offered to God for sin.” The first reference to an offering is in Genesis 4:1-5 where Cain and Abel offered something to God for sin. These offerings are seen throughout the Old Testament and in each case the sinner was coming to God to offer a sacrifice (usually an animal). Their offering was never meant to “take away sin”; they looked forward to the supreme sacrifice that would be offered to God for sin when Jesus Christ, the Lamb of God, “offered Himself without spot to God” (Hebrews 9:14) to pay for man’s sin on the cross. The sacrifices offered to God under the law could never save anyone or bring them forgiveness, as we see in Hebrews 10:1 & 11, “For the law, having a shadow of good things to come, and not the very image of the things, can never with these sacrifices, which offer continually year by year, make those who approach perfect….And every priest stands ministering daily and offering repeatedly the same sacrifices, which can never take away sins.” But then we read in verse 12, “But this Man, after He had OFFERED ONE SACRIFICE FOR SINS, forever sat down at the right hand of God.” So, an OFFERING is a sacrifice made to God, unlike a TITHE which was given to priests to support them, and unlike a PLEDGE which was given to a lender as a guarantee that they would pay them.  (DO)  (553.3)