Ibn al-Qayyim (رحمه الله) said:[1]
And the truthfully insightful person takes a share of every spoils (of war), and associates with every group in the best way possible. He does not favour one group over another and completely avoid the other, as if it has no share of the truth with it. This is the way of the truthful, and the call of Jāhiliyyah (of bigotry and partisanship) is latent in the souls.
The context of this statement from Ibn al-Qayyim pertains to the irādah (wish, desire) of a servant, and how the one who is truthful in his irādah, who has the light of faith in his heart, can arrive at knowledge, truth and right conduct without a great deal of study in particular matters (without making this a generalisation to all knowledge). This is because he is guided to such affairs by his truthfulness.
He (رحمه الله) mentions some groups such as those who concentrate on purification of the soul and refinement of manners, and the Qurʾān reciters who focus on precision in worship, and excess therein, and which of these groups are better company.
So he says that truthfully insightful person is the one who takes from every spoil of war, and associates with all, seeking to take the truth that they have with them.
This is not in reference to the People of Innovations and Misguidance, but in relation to Ahl al-Sunnah, since among them are those who are focused or dedicated to different areas or aspects of religion. For example, some are engrossed in charity work, otherwise are engrossed in purification of the soul, others on manners, others are engrossed in worship, others in daʿwah to Islām and Sunnah and so on, and hence, each carries certain traits and aspects of the truth, more than others.
So which of these is best for a person? THe reality is that he takes from every spoil of war, meaning he benefits from all, because he acquires different aspects of truth and traits from them. So this is the general gist of this statement.
Taking this further in its application, there are associations and friendships on account of locality and familiarity, and thus, there are groups of scholars, or groups of Ahl al-Sunnah in different countries, or locations. The insightful truthful person does not show bigotry to any group, but maintains association with every group in a good way, knowing that truth can be found with them and spoken by them in particular matters, in which it may not be found with other than them, due to their lack of knowledge or familiarity therein, or because it is of no concern to them, or because they are not grounded in the subject matter and so on.
So with this approach, a person does not compromise his access, or his pathways to truth in affairs of religion, because he operates on the principle of taking the truth from whoever presents it with its evidences, and not on partisanship to statuses, personalities, or group loyalties.
As for taking knowledge from everybody, as in seeking it from every party or faction, from Ahl al-Bidʿah and Ahl al-Sunnah, then this is not the way of the truthfully insightful person, because this is an avenue of misguidance. Rather, only Ahl al-Sunnah are sought and studied with, but as for truth that comes incidentally to a person from others, then it is accepted because it is the truth.
See: Shaykh Ibn ʿUthaymīn: Study Only With the People of Truth and Accept Truth From Whomever It Comes.