This phrase is not slang, but rather a proverb which translates to 'He who sows, harvests'. It means that the actions one takes have consequences, whether good or bad, much like planting a seed and then reaping the fruits of that plant later.
Examples
- Spanish: Siempre le decía a mi hijo, el que siembra, cosecha. Si haces buenas acciones, recibirás cosas buenas a cambio.
- English: I always told my son, he who sows, harvests. If you do good actions, you will receive good things in return.