Did Jeremiah curse procrastinators?
God on many occasions commanded his people the Israelites to take hand in the destruction of the pagan sinners, He used them as executioners, such wars were theocratic wars for they were fighting for their God
Nehemiah 4:20 NASB
20 At whatever place you hear the sound of the trumpet, assemble to us there. Our God will fight for us.”
Joshua 10:14 ,42 NASB
14 There was no day like that before it or after it, when the Lord
listened to the voice of a man; for the Lord fought for Israel. 42
Joshua captured all these kings and their lands at one time, because
the Lord, the God of Israel, fought for Israel.
Exodus 14:14 NASB
14 The Lord will fight for you, while you keep silent.”
As in King Saul’s case, the sin would lie in not carrying out orders to the pleasing of God; as it is written in Jeremiah.
Jeremiah 48:10 NASB
10 Cursed is the one who does the Lord’s work negligently, And cursed
is the one who restrains his sword from blood.
Evidently, Saul’s sin consisted of his presumptuously going ahead with the sacrifice and not obeying God's commandment, which had been given through his representative Samuel, to wait for Samuel to offer up the sacrifice. (1 Samuel 10:8, 1 Samuel 13: 1-14 )
Conclusion.
I do not know Hebrew, but based on the meaning of the text, the proper meaning is
"negligently,"