Hi CanIhunt,
We need to consider the context of those verses you asked about.
Consider Mark 4:11-25 to help in understanding.
Mark 4:11-25
And He said to them, “To you (Christians) it has been given to know the mystery of the kingdom of God; but to those who are outside (non believers), all things come in parables, so that
‘Seeing they may see and not perceive,
And hearing they may hear and not understand;
Lest they should turn,
And their sins be forgiven them.’”
And He said to them, “Do you not understand this parable? How then will you understand all the parables? The sower sows the word (the gospel). And these are the ones by the wayside where the word is sown.
When they hear, Satan comes immediately and takes away the word that was sown in their hearts. These likewise are the ones sown on stony ground who, when they hear the word, immediately receive it with gladness; and they have no root in themselves, and so endure only for a time. Afterward, when tribulation or persecution arises for the word’s sake, immediately they stumble. Now these are the ones sown among thorns; they are the ones who hear the word, and the cares of this world, the deceitfulness of riches, and the desires for other things entering in choke the word, and it becomes unfruitful. But these are the ones sown on good ground, those who hear the word, accept it, and bear fruit: some thirtyfold, some sixty, and some a hundred.”
Also He said to them, “Is a lamp brought to be put under a basket or under a bed? Is it not to be set on a lampstand? For there is nothing hidden which will not be revealed, nor has anything been kept secret but that it should come to light. If anyone has ears to hear, let him hear.”
Then He said to them, “Take heed what you hear. With the same measure you use, it will be measured to you; and to you who hear, more will be given. For whoever has, to him more will be given; but whoever does not have, even what he has will be taken away from him.
We can see from the context that it speaks of the gospel of Christ. Believe on Jesus and you will be saved. Christians are saved by grace.
And as Christians we are to let our light (Christ in us) shine, preaching the gospel of Christ to the lost.
And note Matt 5:15, 16 which also speaks of the light on the lamp-stand.
Nor do they light a lamp and put it under a basket, but on a lampstand, and it gives light to all who are in the house. Let your light (Christ in us) so shine before men, that they may see your good works (our works are to believe on Jesus, John 6:29) and glorify your Father in heaven.
And note Mark 4:24
Take heed what you hear. With the same measure you use, it will be measured to you;
Note 7:1-3
“Judge not, that you be not judged. For with what judgment you judge, you will be judged; and with the measure you use, it will be measured back to you. And why do you look at the speck in your brother’s eye, but do not consider the plank in your own eye?
If we measure one's righteousness by works of the law ( as the Pharisees did) then that's the same measure by which we will be judged.
But if we use the measure of grace/love (as Jesus commanded us to love one anther) then we will be measured by that same measure of grace/love.
Therefore we are to take heed to what we hear.
We are to avoid any false doctrine that preach righteousness by works of the law.
As Christians we're saved by grace. Therefore we should not mix works of the law, with grace.
Rom 11:6
And if by grace, then it is no longer of works; otherwise grace is no longer grace. But if it is of works, it is no longer grace; otherwise work is no longer work
Or as Jesus put it in Matt 16:6
Then Jesus said to them, “Take heed and beware of the leaven of the Pharisees and the Sadducees.”
What is the leaven?
Matt 16:12
Then they understood that He did not tell them to beware of the leaven of bread, but of the doctrine of the Pharisees and Sadducees.
The doctrine of the Pharisees and Sadducees was righteousness by works of the law. This is what we need to take heed of in what we hear. Always remember that it's by grace that we're saved. Believe on Jesus and thus our faith is counted for righteousness, Rom 4:5.