註四十二章經 1.291

1.291

言沙門直心行道，欲出生死苦海，須念念相應，勿起妄念。如牛負重，於深泥中求避泥淖，以自蘇息，亦念念憂懼，不敢左右顧也。

This means that when a śramaṇa practices the Way with a straightforward mind, desiring to emerge from the ocean of suffering that is birth and death, thought-moment must follow thought-moment in accord, without giving rise to vain thoughts. Like an ox carrying a heavy load seeking to escape the slough in deep mud so as to catch its breath, anxious and fearful at every moment, not daring to look left or right.