Deuteronomy 1:42-45 And the LORD said unto me, Say unto them, Go not up, neither fight; for I am not among you; lest ye be smitten before your enemies. So I spake unto you; and ye would not hear, but rebelled against the commandment of the LORD, and went presumptuously up into the hill. And the Amorites, which dwelt in that mountain, came out against you, and chased you, as bees do, and destroyed you in Seir, even unto Hormah. And ye returned and wept before the LORD; but the LORD would not hearken to your voice, nor give ear unto you.
Disaster is the ultimate consequence of presumptuous undertakings. The Israelites first wouldn't go fight when the Lord said to fight. Then, when they found out what would happen, they decided they would go to battle after all. Unfortunately for them, by then it was too late. They decided they didn't need the Lord's blessing, went anyway, and got beat up.
This is the first type of presumptuous undertakings. If the Lord says go do it, you better go. If He says don't go do it, you better not go. To presumptuously act directly against His command is to take a sure road to disaster.
2 Samuel 4:8-11 And they brought the head of Ishbosheth unto David to Hebron, and said to the king, Behold the head of Ishbosheth the son of Saul thine enemy, which sought thy life; and the LORD hath avenged my lord the king this day of Saul, and of his seed. And David answered Rechab and Baanah his brother, the sons of Rimmon the Beerothite, and said unto them, As the LORD liveth, who hath redeemed my soul out of all adversity, When one told me, saying, Behold, Saul is dead, thinking to have brought good tidings, I took hold of him, and slew him in Ziklag, who thought that I would have given him a reward for his tidings: How much more, when wicked men have slain a righteous person in his own house upon his bed? shall I not therefore now require his blood of your hand, and take you away from the earth?
David had a little problem with some of his mighty men. It seems they tended to go off on their own and do some things that they thought would please David. The problem was, David never gave them the authority to do those things. When he found out, those who had presumed to act for David without his blessing ended up with the blood on their heads.
Presumptuous undertakings are not just doing things directly against the Lord's wishes. Any attempt to go out on our own without explicit authority is another type of presumption and gets you the same reward as directly violating the Lord's commands. Claiming that you thought you were doing a good thing for the Lord is no excuse. It may be it was something the Lord wanted doing, but He decides when and where the deed gets done. We work according to His timetable and His plan and we are not to presume the authority to interfere with that plan no matter what our motivations are.
Matthew 16:21-23 From that time forth began Jesus to shew unto his disciples, how that he must go unto Jerusalem, and suffer many things of the elders and chief priests and scribes, and be killed, and be raised again the third day. Then Peter took him, and began to rebuke him, saying, Be it far from thee, Lord: this shall not be unto thee But he turned, and said unto Peter, Get thee behind me, Satan: thou art an offence unto me: for thou savourest not the things that be of God, but those that be of men.
Now Peter was the disciple that tended to be rather spontaneous. When Jesus asked his disciples, "whom say ye that I am?" (Matthew 16:15), it was Peter that jumped right in and declared, "Thou art the Christ, the Son of the living God." (v. 16) In return, Jesus gave Peter enormous praise and declared that only God could have revealed this knowledge to Peter. I guess the praise got Peter to thinking he knew everything he needed to know about Jesus, because it wasn't too much later that Peter opens his big mouth and has to be severely rebuked by Jesus. That's presumption again. Peter thinks he knows it all and to his embarrassment finds out it just wasn't so.
We don't presume to declare to our Lord what He should do. We are the servants and follow His commands, not the other way around. When He asks us a question, we respond. When He declares His will to us, we listen, accept it and are not to think we know better. That would be another presumptuous undertaking.
1 Corinthians 12:4-11 Now there are diversities of gifts, but the same Spirit...But the manifestation of the Spirit is given to every man to profit withal. For to one is given by the Spirit the word of wisdom; to another the word of knowledge by the same Spirit; To another faith by the same Spirit; to another the gifts of healing by the same Spirit; To another the working of miracles; to another prophecy; to another discerning of spirits; to another divers kinds of tongues; to another the interpretation of tongues: But all these worketh that one and the selfsame Spirit, dividing to every man severally as he will.
Each of us is given certain gifts, and all of the gifts of the spirit work for the glory of God. What we must always remember is that some have one gift and others have another gift. Along with each gift there is the appropriate calling. So long as each gladly takes the gift he receives and follows the calling appropriate to that gift, the entire body of Christ benefits.
Unfortunately there seems to be this tendency among Christians to want to decide what gift we would like to have. Someone wants to be prophet, a teacher, or a man of knowledge, (usually out of envy and pride), declares themselves so, and then proceeds to utter a string of nonsense. This is yet another presumptuous undertaking. We must diligently pray and ask the Lord what our calling is and wait for Him to reveal it to us. Then, when the revelation of that calling comes, be thankful and stick to it. If we try to become something we have no gift for, all we do is end up in misery. It is the Lord's giving, choosing and calling not ours.
Just as important is to not presume that everyone's calling is the same as our own. Because certain gifts are bestowed on someone, they may have the ability to do things another should not attempt to do. We must not presume that because something is outside our own calling that it is therefore outside everyone else's as well. As Proverbs 18:16 says, "A man's gift maketh room for him." So, each should do as his gift allows and not condemn others whose gifts are different. We are all one body, but are not all the same.
The uniqueness of each is to the glory of God as He manifests His infinite nature through us all. So long as we stay within His will, wait to hear His voice, keeping to the path He sets before us, and avoiding all the presumptuous undertakings, He remains with us always. Then, by His spirit all our undertakings are sure to be blessed.