1.45
"Bhikkhus, suppose there is a lake that is murky, stirred up, and full of mud. A person with good eyesight standing on the shore would not be able to see the shells, gravel, or fish moving or staying still beneath the surface. Why is that? Because the water is murky. In the same way, it is impossible for a bhikkhu with a murky (an unclear, cloudy, agitated, or disturbed) mind to understand their own welfare, the welfare of others, or the welfare of both, or to realize the distinction in wisdom and vision worthy of the noble ones. Why is that? Because the mind is murky."
1.46
"Bhikkhus, suppose there is a lake that is clear, calm, and ripple-free. A person with good eyesight standing on the shore would be able to see the shells, gravel, or fish moving or staying still beneath the surface. Why is that? Because the water is clear. In the same way, it is possible for a bhikkhu with a clear (still, tranquil, undisturbed) mind to understand their own welfare, the welfare of others, or the welfare of both, and to realize the distinction in wisdom and vision worthy of the noble ones. Why is that? Because the mind is clear."
Related Teachings:
Teachings on the harmful and beneficial qualities (AN) ↗️ - In this teaching on contrasting pairs, the Buddha shares that harmful qualities when pursued, lead to one's decline in morality, generosity, faith, concentration, and wisdom.
Beings come together and associate based on dispositions (SN 14.15) - In this teaching, the Buddha is sharing how beings come together and associate based on shared qualities and traits.
The defining characteristic of living beings (SN 23.2) - Rādha asks the Buddha about a the term "being", and the Buddha explains in terms of craving for the five aggregates. He compares such craving to a child playing with sandcastles.
