Nadab and Abihu, sons of Aaron, had seen all that God had done and been part of it, but wanted their own way of doing things. A legacy of meeting with God will not keep you in relationship with God! Only a relationship grounded in truth will do!
Their fire was profane because it was initiated from the atoning and redeeming work of sacrifice. There is a huge difference between the fire kindled by God and fire conjured up by man. Even Satan can conjure fire as he does in Rev 13.
“Before the Lord” probably meant they went past the curtain into the Most Holy Place.
Fire from God can be fire of glory and judgement – the same fire!
David’s friends want him to flee like a bird to the mountains to get away from Saul – but that is not David’s way. “He would rather dare the danger than exhibit a distrust in the Lord his God.” (Spurgeon) It was well meaning advice, like Peter’s to Jesus (Don’t go to the cross!) but it was ungodly.
The answer is to acknowledge God is in the Temple on the Throne!
1 Thess 4
God’s will is our sanctification!